The sub-umbral cavity (s.c.) functions as a brood-space for the developing embryos, which are set free by rupture of the wall.
In this way over a hundred embryos may result from a single egg.
The eggs of the female give rise to embryos within the body of the mother; her other organs undergo a retrogressive change and serve as food for the young, until the body-wall only of the mother remains as a brown capsule.
The arrested embryos or eggs are then swallowed and digested by those in the same capsule which have advanced in development.
The embryos in the uterus are all nearly of the same age, except for a month or two before birth, when two broods overlap.
In some embryos there is but a single pair of these rudiments (or vestiges) situate on the first abdominal segment, and in some cases they become invaginations of a glandular nature.
Nevertheless, though the conceptions originally denoted by " evolution " and " development " were shown to be untenable, the words retained their application to the process by which the embryos of living beings gradually make their appearance; and the terms" development," " Entwickelung,"and " evolutio " are now indiscriminately used for the series of genetic changes exhibited by living beings, by writers who would emphatically deny that " development " or " Entwickelung " or " evolutio," in the sense in which these words were usually employed by Bonnet or Haller, ever occurs.
Some species of Botrychium have recently been found to have embryos provided with a suspensor.
The following species are aberrant in respect of these characters: Peripatus (Opisthopatus) cinctipes, Purcell (Cape Colony and Natal), presents a few Australasian features; there is a small receptaculum seminis on each oviduct, some of the legs are provided with welldeveloped coxal organs, the feet have one anterior, one posterior and one dorsal papilla, and the successive difference in the ages of the embryos in the uterus, though nothing like that found in the neotropical species, is slightly greater than that found in other investigated African species.
- Embryos of Springtail (Anurida maritima).
p, Lips of redia; q, collar; r, processes serving as rudimentary feet; s, embryos; 1, trabecula crossing body-cavity of redia; u, glandular cells; v, birth-opening; w, w', morulae; y, oral sucker; y', ventral sucker; z, pharynx.
Only the embryos of Leptodora are known to hatch out in the nauplius stage.
The uterus appears to contain embryos of different ages.
bancrofti is known to live in the lymphatic glands, and its embryos Microfilaria sanguinis hominis nocturna, passing by the thoracic duct, reach the blood-vessels and circulate in the blood.
In the embryos of many insects there are projections from the segments of the abdomen similar, to a considerable extent, to the rudimentary thoracic legs.
The embryos are free-swimming, active forms, but in adult life the animals are fixed head downwards, and are very degenerate.
In Coelebogyne (Euphorbiaceae) and in Funkia (Liliaceae) polyembryony results from an adventitious production of embryos from the cells of the nucellus around the top of the embryo-sac. In a species of Allium, embryos have been found developing in the same individual from the egg-cell, synergids, antipodal cells and cells of the nucellus.
Vernon have adduced experimental evidence as to the induction of variation by such causes as difference in the ages of the parents, in the maturity or freshness of the conjugating germ cells, and in the condition of nutrition for the embryos.
At the end of a fortnight the white spat has become darkcoloured from the appearance of coloured patches in the developing embryos.
The embryos having then reached the condition of "trochospheres" escape from the mantle cavity and swim about freely near the surface of the water among the multitude of other creatures, larval and adult, which swarm there.
A few cases are known in which the developing embryos are nourished by a special secretion while in the brood-chamber of the mother (Cladocera, terrestrial Isopoda).
The mollusc reciprocates by throwing off its embryos on the parent fish, in the skin of which they remain encysted for some time, the period of reproduction of the fish and mussel coinciding.
In the Abietineae the cells of the middle tier elongate and push the lowest tier deeper into the endosperm; the cells of the bottom tier may remain in lateral contact and produce together one embryo, or they may separate (Pinus, Juniperus, &c.) and form four potential embryos.
altissima, the fertilized eggs grow into tubular proembryos, from the tip of each of which embryos begin to be developed, but one only comes to maturity.
17, C, z and z'); they then grow into long tubes or proembryos, which make their way towards the prothallus (C, z'), and eventually embryos are formed from the ends of the proembryo tubes.
After the egg-cells have been fertilized by the non-motile male cells they grow into tubular proembryos, producing terminal embryos.
Now comes a great change, unfortunately difficult to follow whether in the fossils or in the modern embryos.
A highly specialized means of vegetative reproduction is seen in the tubers of Phylloglossum and the embryos of some Lycopods.
In these cocoons are deposited the eggs together with a certain amount of albumen upon which the developing embryos feed.
In most of the African species, however, the embryos of the uterus are almost of the same age and are born at a definite season.
- A Series of Embryos of P. capensis.
The hind end of embryos B, C, D is uppermost in the figures, the primitive streak is the white patch behind the blastopore.
- A series of diagrams of transverse sections through Peripatus embryos to show the relations of the coelom at successive stages.
Embryos in the uterus of very different ages, and probably born all the year round.
Ova large, with much yolk and thick membrane, like those of Australasian species; embryos with slit-like blastopore and of very different ages in the same uterus, probably born all the year round.
Such forms he distinguished as Coelentera, and showed that they had no special affinity with echinoderms, polyzoa, &c. He divided the Coelentera into a group Hydrozoa, in which the sexually produced embryos were usually set free from the surface of the body, and a group Actinozoa, in which the embryos are detached from the interior of the body and escape generally by the oral aperture.
2 The three metatarsals in the penguins are not, as in other birds, united for the whole of their length, but only at the extremities, thus preserving a portion of their originally distinct existence, a fact probably attributable to arrest of development, since the researches of C. Gegenbaur show that the embryos of all birds, so far as is known, possess these bones in an independent condition.
Developmental effects of glufosinate ammonium on mouse embryos in culture.
As previously described, CAH embryos are exposed to excess androgens from the first few weeks, right through until birth.
balancer chromosomes carry lethal or sterile mutations, so only the heterozygous embryos develop into fertile adults, allowing propagation of the balanced stock.
blastocyst embryos that are used for stem cell isolation can be grown in vitro from embryos produced by IVF.
The scientific establishment is not mentioning the embryos created, only to be destroyed in the process of extracting embryonic stem cells.
Ten fertility clinics in the UK are licensed to test embryos.
clone embryos in order to make ends meet!
creation of human embryos for experimentation.
In November 2001 a judicial review ruled that creating cloned human embryos lay outwith the strict definition of embryos in the Act.
destruction of embryos as a matter of course.
donatepril 2005, the law surrounding donating sperm, eggs or embryos was changed.
So they arranged to produce a number of fertilized embryos which were tested for compatibility with their daughter's DNA.
Zebrafish embryos with a mutation called gridlock show faulty development of blood vessels in the lower portion of the body.
We're reviving frozen embryos right now, for instance.
Claims to have created both cloned and parthenogenetic human embryos in November seem to have been premature.
It is possible to remove cells from early pre-implantation embryos without damage to the original embryo.
This approach has worked very well for other types of molecules studied in frog embryos.
The axolotl is a salamander, and many of the fundamental discoveries in vertebrate embryology came from studies of axolotl embryos.
He has consistently opposed human cloning, eugenics, coercive population polices, abortion, destructive experiments on human embryos and euthanasia.
Methods These experiments were performed on tissue explants or brain slices prepared from mouse embryos and pups from development stages E15 through P20.
fertility clinics in the UK are licensed to test embryos.
Coryne, a common British longed into a brood pouch conhydroid, produces gonophores; taining embryos.
The spadix forms a gelatinous cyst, the so-called acrocyst (ac), external to the gonotheca (gth), enclosing and protecting the embryos.
These are reduced, in all birds, to three, but traces of the fourth have been observed in embryos.
He is also studying how germ cell determining mechanisms evolved in vertebrate embryos.
We should be careful not treat human embryos with less respect than animals.
But surprisingly, mice embryo fibroblasts (MEFs) derived from these embryos proliferated normally and ERK activation was also completely normal.
When injected as synthetic mRNA, its protein emits intense fluorescence in living embryos.
freezeitu conservation of genetic resources, by holding breeding groups in zoos or as embryos frozen in genebanks, is effective but too costly.
frozen embryos right now, for instance.
Abstract. cDNAs specific to vegetal poles of Xenopus gastrula embryos were used as a probe to screen a gastrula embryos were used as a probe to screen a gastrula vegetal pole cDNA library.
In the latest research, scientists inserted a gene for a single protein produced by BDV into mouse embryos.
Once pregnant they cease to feed for the 3 to 4 month gestation period whilst the embryos develop inside the body.
There would be a ban on commercial surrogacy, putting human embryos in animals and vise versa, and the creation of human-animal hybrids.
Like all mammals, mouse embryos are relatively inaccessible within the mother.
injected into silkworm embryos.
inserted a gene for a single protein produced by BDV into mouse embryos.
manipulation of early human embryos in similar fashion, to reproduce results done in animal experiments, would be completely unethical.
Contrary to the United States, Switzerland bans the donation of eggs and human embryos, and also bans surrogate motherhood.
notochord differentiation, leading to embryos of significantly diminished stature.
There were no significant differences in mean age, number of mature oocytes obtained, and number of embryos transferred between the two groups.
Last November, the HFEA launched a public debate on testing embryos for ' lower penetrance ', late onset genetic disorders.
He was an enthusiast for evolution and saw in the growth of embryos what he called ' ontogeny recapitulates phylogeny ' .
That seems to me to be morally preferable than throwing away embryos that you can't use in an IVF program.
Using human embryos is opposed in the name of 'the sanctity of life ', or because embryos are potential human beings.
In April 2005, the law surrounding donating sperm, eggs or embryos was changed.
The HFEA will not license research projects involving embryo splitting with the intention of increasing the number of embryos for transfer.
obtaining stem cells from umbilical cords is far less controversial than sourcing them from embryos (as many scientists would like to do ).
stem cells from umbilical cords is far less controversial than sourcing them from embryos (as many scientists would like to do ).
storage of gametes (eggs and sperm) and embryos.
surplus embryos produced throughout the world in the course of infertility treatment.
Generally two healthy embryos are put into the mothers womb.
011ulanus tricuspis is found in the adult state in the alimentary canal of the cat; the young worms are hatched in the alimentary canal, and often wander into the body of their host and become encysted in the lungs, liver and other organs; during the encystment the worm degenerates and loses all trace of structure.` This wandering appears to be accidental, and to have nothing to do with the further evolution of the animal which takes place in those embryos which are voided with the excrement.
The co-existence of the asexual encysted form and the sexually mature adult in the same host, exceptionally found in 011ulanus and other Nematodes, is the rule in Trichinella; many of the embryos, however, are extruded with the faeces, and complete the life cycle by reaching the alimentary canal of rats and swine which frequently devour human ordure Swine become infested with Trichinella in this way and also by eating the dead bodies of rats, and the parasite is conveyed to the body of man along with the flesh of "trichinized" swine.
If we assume that each female produces 300 embryos, and that half of these are females, the number of descendants would be, after six generations, some 22,781 milliards (A.
41, B), where, however, the tentacles have quite disappeared, and the circular rim formed by the margin of the umbrella has nearly closed over the manubrium leaving only a small aperture through which the embryos emerge.
Then the spadix withers, leaving the embryos in the acrocyst, which may be further protected by a so-called marsupium, a structure formed by tentacle-like processes growing out from the blastostyle to enclose the acrocyst, each such process being covered by perisarc like a glove-finger secreted by it (fig.
Accordingly, the shell of Aplysia must not be confounded with a primitive shell in its shell-sac, such as we find realized in the shells of Chiton and in the plugs which form in the remarkable transitory " shell-sac " or " shell-gland " of Molluscan embryos (see figs.
Marchal points out the analogy of this phenomenon to the artificial polyembryony that has been induced in Echinoderm and other eggs by separating the blastomeres, and suggests that the abundant food-supply afforded by the host-larva is favourable for this multiplication of embryos, which may be, in the first instance, incited by the abnormal osmotic pressure on the egg.
In Anodonta, as in many other Lamellibranchs, the ova and hatched embryos are carried for a time in the ctenidia or gill apparatus, and in this particular case the space between the two lamellae of the outer gill-plate is that which serves to receive the ova (fig.
In the Ostrea edulis fertilization of the eggs is effected at the moment of their escape from the uro - genital groove, or even before, by means of spermatozoa drawn into the sub-pallial chamber by the incurrent ciliary stream, and the embryos pass through the early stages of development whilst entangled between the gill-lamellae of the female parent (fig.
Genes of interest were introduced into mouse embryos alongside a " reporter gene " that produces a fluorescent substance wherever the gene is active.
The leaflet, Avoiding Multiple Births - deciding how many embryos to transfer, informs patients about the risks associated with multiple births.
Obtaining stem cells from umbilical cords is far less controversial than sourcing them from embryos (as many scientists would like to do).
The HFEA also regulates the storage of gametes (eggs and sperm) and embryos.
They are obtained from surplus embryos produced throughout the world in the course of infertility treatment.
Embryos are created in a test tube from the mothers eggs and the fathers sperm.
By using PGD, couples at risk of having a child with CF can undergo IVF, and then implant only unaffected embryos.
We will consider some real data from studies on 2 vertebrate embryos.
In my anatomy class, we looked at photos of the amnia to learn about the development of embryos.
Comparing the amnia of mammals, birds, and reptiles shows us that embryos can develop in different ways.
During the first two weeks, the fertilized eggs, aka blastocytes, develop into embryos.
By week three, the embryos are well on their way to developing their organs.
By the end of the fourth week, it is usually possible for a veterinarian to feel the pea sized embryos by palpating the uterus.
The embryos can usually be felt at 28 days after the breeding.
An ultrasound would allow your vet to see any developing embryos.
Fraternal twins are referred to as dizygotic twins, meaning that two unions of two gametes or male/female sex cells occurred to produce two separate embryos.
The implantation of several embryos and placentas in the endometrium of the uterus results in a competition for space and inevitably some implant in an area without good circulation.
The chance of multiple gestation with in vitro fertilization (IVF) is about the same as with the use of fertility drugs, because several embryos are inserted into the womb to increase the odds of conception.
With the use of assisted reproductive technology, an ultrasound is usually performed with ten days to see if any of the embryos were successful with implantation, and a multiple gestation would be revealed at that time.
They have transplanted bone marrow cells into living embryos in the uteri of animals to approach congenital diseases, birth defects, and mental retardation.
Embryonic stem cells are derived from human embryos.
Also, some vaccines, including those for influenza, measles, and mumps, are grown in the laboratory in fluids of chick embryos, and should not be given to children who are allergic to eggs.
Only the embryos unaffected by the disease are transferred back into the uterus.
PCEC is made from rabies virus grown in cultures of chicken embryos and then inactivated.
Children who are allergic to eggs should not be give vaccines cultured in chicken embryos.
Cryopreservation, or freezing, of eggs and/or embryos, is a method used to help women overcome secondary infertility and cancer survivor issues.
Donor Embryos: This infertility treatment utilizes frozen embryos, often ones that are excess from another couple undergoing IVF.
Embryo storing: Some couples may choose to have their eggs and sperm combined in a lab, created embryos that are frozen.
The embryos are later implanted into the uterus via IVF.
So if you want a boy, have the doctor only implant the male embryos.
This information gives the reader some general information about how many procedures have been conducted, how many used fresh embryos and frozen ones, as well as the percentage of clinics offering services to single women.
The percentage of IVF cycles resulting in pregnancies is listed, as well as the average number of embryos transferred during each cycle.
If the embryos are developing normally, one or two of them will be transferred into the uterus.
The physician uses a catheter to move the embryos through the cervix and into the uterus for development.
Women who are older than 35 might have more than one or two embryos transferred.
The infertility specialist may freeze additional fertilized embryos in case a future treatment cycle is necessary.
By a simple modification, the open pit becomes a solid ectodermal ingrowth, just as in Teleostean fishes the hollow medullary tube, or the auditory pit of other vertebrate embryos, is formed at first as a solid cord of cells, which acquires a cavity secondarily.
Thus in Erythronium and Limnocharis the fertilized egg may form a mass of tissue on which several embryos are produced.
Mammalian embryos have to implant into the mothers womb in order to grow properly.
c.c., embryos are hatched in an in early stage, but their meta- ov, morphosis has not been plch, observed.
The fertilized egg-cell (oospore) forms a filamentous structure, the proernbryo, from a restricted basal portion of which one or more embryos develop, one only as a rule reaching maturity.
Rabl has with remarkable skill applied the method of sections to the study of the minute embryos of Planorbis.
Other Pulmonata possess, when embryos, Stiebel's canals in a more fully developed state, for instance, the common slug Limax.
Wheeler (1893) and others in various insect embryos, while in the lowest insect order - the Aptera - a pair of minute jaws - the maxillulae - in close association with the tongue are present, as has been shown by H.
No doubt can be entertained that the greater part of the inner layer corresponds to the mesoderm of more ordinary embryos, for the coelomic pouches, the germ-cells, the musculature and the vascular system all arise from it.
Wheeler (1889) on the embryos of two beetles - Hydrotails Lepisma and Machilis, an interesting transitional condition philus and Doryphora respectively.
Lecaillon (1898) on various leaf beetles, tend to show that the organ " in the embryos of the lower Arthropoda corresponds with whole of the " mid-gut " arises from the proliferation of cells at the the region invaginated to form the serosa of the hexapod embryo.
Occasionally the power of reproduction is thrown still farther back in the life-history, and it is found that from a single egg a large number of embryos may be formed.
Thus a mass or chain of embryos is produced, lying in a common cyst, and developing as their larval host develops.
If they fall on pasture land or fodder of any kind and are eaten by any herbivorous animal, such as a hare, rabbit, horse, sheep or ox, the active embryos or larvae are set free in the alimentary canal of the new host.
Here the eggs are fertilized and here they segment so that the young embryos are formed within their mother's 9 body.
The embryos escape into the uterus through the "bell," a funnellike opening continuous with the uterus.
m The "bell" swallows the matured embryos and passes them on into the uterus, and thus out of the body via the oviduct, which opens at one end into the uterus and at the other on to the exterior at the posterior end of o.-- the body.
But should the "bell" swallow any of the ova, or even one of the younger embryos, these are passed back into the body cavity through the second and dorsal opening.
von Baer in 1828, 5 Muller calls the attention of naturalists to the important fact, that while all the Squamata possess an amnion and an allantois, these structures are absent in the embryos of all the Nuda.
All segments passed should be burnt, and they should never be thrown where the embryos may become scattered.
In the case of filariasis due to Filaria bancrofti, which is common throughout the Tropics, the embryos of the parasite are disseminated by various Culicinae and Anophelinae (Culex pipiens in Queensland; C. fatigans in the West Indies; Myzomyia rossii in India; Pyretophorus costalis in a large portion of tropical Africa; &c.).
The ovicells are modified zooecia, and contain numerous embryos which in the cases so far investigated arise by fission of a primary embryo developed from an egg.
Embryos in the second stage, if artificially released from the uterus, are able to live in water, in the same way as similarly developed larvae of S.
Medusae, when they reproduce themselves by budding, always produce medusae, but when they reproduce by the sexual method the embryos produced from the egg grow into medusae in some cases, in other cases into polyps which bud medusae in their turn.
A single otolith is present as in the veliger embryos of Opisthobranchia.
Cycladidae.-One siphon or two free siphons with simple orifices; pallial line simple; hermaphrodite, embryos incubated in external gill-plate; freshwater, Cyclas; British.
If, on the other hand, the endosperm is the product of an act of fertilization as definite as that giving rise to the embryo itself, we have to recognize that twin-plants are produced within the embryo-sac - one, the embryo, which becomes the angiospermous plant, the other, the endosperm, a short-lived, undifferentiated nurse to assist in the nutrition of the former, even as the subsidiary embryos in a pluri-embryonic Gymnosperm may facilitate the nutrition of the dominant one.
The worm inhabits the lung of the frog and toad, and is hermaphrodite (Schneider) or parthenogenetic (Leuckart); the embryos hatched from the eggs find their way through the lungs into the alimentary canal and thence to the exterior; in a few days they develop into a sexual larva, called a Rhabditiform larva, in which the sexes are distinct; the eggs remain within the uterus, and the young when hatched break through its walls and live free in the perivisceral cavity of the mother, devouring the organs of the body until only the outer cuticle is left; this eventually breaks and sets free the young, which are without teeth, and have therefore lost the typical Rhabditis form.
Medusae, so-called " meconidia," are budded but not liberated; each in turn, when it reaches sexual maturity, is protruded from the gonotheca by elongation of the stalk, and sets free the embryos, after which it withers and is replaced by another (Allman , p. 57, fig.
Ova minute, with little food-yolk; embryos in the uterus at very different stages of development.
in diameter, with little yolk, and the embryos provided with large trophic vesicles (Willey).
The word usage examples above have been gathered from various sources to reflect current and historial usage. They do not represent the opinions of YourDictionary.com.