We have analogies to this in the two nuclei of some of the protozoa, the one being solely for the purpose of propagation, the other being associated with the functional activities of the cell.
Thus, to begin with, the animal pedigree is divided into two very distinct grades, the Protozoa and the Metazoa.
GASTROTRICHA, a small group of fairly uniform animals which live among Rotifers and Protozoa at the bottom of ponds and marshes, hiding amongst the recesses of the algae and sphagnum and other fresh-water plants and eating organic debris and Infusoria.
The chromatin is distributed throughout the cytoplasm in the form of granules which may be regarded as a distributed nucleus corresponding to what Hertwig has designated, in protozoa, chromidia.
' Classes: Rotifera, Polygastria (the Protozoa of recent authors).
"Protozoa" in Ency.
- Scaphopoda feed on the lowest marine organisms such After Kowalewsky, in Lanas Diatoms, Protozoa, &c. There are 150 's Treatise on Zoology, living and about 275 known fossil species.
Anatomic, Berlin, 1845) as that of a primary division of animals, the others recognized in that treatise being Protozoa, Zoophyta, Vermes, Mollusca and Vertebrata.
Linnaeus applied the Latin term Vermes to the modern zoological divisions Mollusca, Coelentera, Protozoa, Tunicata, Echinoderma (qq.v.), as well as to those forms which more modern zoologists have recognized as worms. As a matter of convenience the term Vermes or Vermidea is still employed, for instance in the International Catalogue of Zoological Literature and the Zoological Record, to cover a number of wormlike animals.
Milne-Edwards removed the Polyzoa; the group was soon further thinned by the exclusion of the Protozoa on the one hand and the Entozoa on the other; while in 1848 Leuckart and Frey clearly distinguished the Coelenterata from the Echinodermata as a separate sub-kingdom, thus condemning the usage by which the term still continued to be applied to these two groups at least.
Animals suffer from the ravages of bot flies (Oestridae) and gad flies (Tabanidae); while the tsetse disease is due to the tsetse fly (Glossina morsitans), carrying the protozoa that cause the disease from one horse to another.
Lime is, in fact, absorbed to an enormous extent by fishes, molluscs, crustacea, calcareous algae and sponges, starfishes, sea-urchins and feather stars, many polyzoa and a multitude of protozoa (mainly the foraminifera).
The structural features which the Mollusca do possess in common with other animals belonging to other great phyla of the animal kingdom are those characteristic of the Coelomata, one of the two great grades (the other and lower being that of the Coelentera) into which the higher animals; or Metazoa as distinguished from the Protozoa, are divided.
Unlike the cells of Protozoa, these embryonic cells of the Metazoa do not remain each like its neighbour and capable of independent life, but proceed to arrange themselves into two layers, taking the form of a sac. The cavity of the two-cell-layered sac or diblastula thus formed is the primitive gut or arch-enteron.
Simple protozoa appear in the form of Radiolaria; Lithistid sponges are represented by such forms as Archaeoscyphia, Hexactinellid sponges by Protospongia; Graptolites (Dictyograptus (Dictyonema)) come on in the higher parts of the system.
From the more complex colonial Protozoa the Coelentera are readily separated by their possession of two distinct sets of cells, with diverse functions, arranged in two definite layers, - a condition found in no Protozoan.
The old criterion by which they and other Metazoa were once distinguished from Protozoa, namely, the differentiation of large and small sexual cells from each other and from the remaining cells of the body, has been broken down by the discovery of numerous cases of such differentiation among Protozoa.
They belong to the group of Protozoa, and, as already explained, have a double cycle of existence: (I) a sexual cycle in the body of the mosquito, (2) an asexual cycle in the blood of human beings.
SPOROZOA, a large and most important section of the Protozoa, all the members of which are exclusively parasitic in habitat.
A great variety of forms were described by other observers, but they were not separated as a class from the unicellular organisms (Protozoa) with which they usually occur, until the appearance of C. G.
The Rotifera are all aquatic, the majority dwelling in fresh water with Protozoa and Protophyta, as well as Entomostracous Crustacea.
Wright, "Protozoa in a case of tropical ulcer (Delhi sore), " Journ.
In comparing algae with the great archegoniate series which has doubtless sprung from them, it is natural to inquire to what extent, if any, they present evidence of the existence Peridiniaceae Diatomaceae Cryptomonadaceae - Hydruraceae - EuPHAEOPHYnEAE Protozoa Flagellata protomastigina...
The existence of ciliated micrococci together with the formation of endospores - structures not known in the Cyanophyceae - reminds us of the flagellate Protozoa, e.g.
Orders: Rotifera, Homogenea (this includes the Protozoa of recent writers and some Protophyta).
Protozoa' (various groups included).
The geographical distribution is cosmopolitan, as is the case with Protozoa and Protophyta of similar habits.
Haeckel himself, with his pupil MikluchoMaclay, had in the meantime made studies on the growth from the egg of Sponges - studies which resulted in the complete separation of the unicellular or equicellular Protozoa from the Sponges, hitherto confounded with them.
These include Protozoa, three sponges, Vermes, twenty-five Molluscs, numerous Amphipods, fishes of the genera Gobius, Benthophilus and Cobitis, and one mammal (Phoca caspia).
On the ether hand, a survey of the facts of cellular embryology which were accumulated in regard to a variety of classes within a few years of Kovalevsky's work led to a generalization, independently arrived at by Haeckel and Lankester, to the effect that a lower grade of animals may be distinguished, the Protozoa or Plastidozoa, which consist either of single cells or colonies of equiformal cells, and a higher grade, the Metazoa or Enterozoa, in which the egg-cell by " cell division " gives rise to two layers of cells, the endoderm and the ectoderm, surrounding a primitive digestive chamber, the archenteron.