Cloaca and Genital Organs.
P. Hill, "Contributions to the Morphology of the Female Urino-genital Organs in Marsupialia," Proc. Linn.
From them are developed two distinct types of histological elements; the genital cells and the cnidoblasts or mothercells of the nematocysts.
The genital cells are simple wandering cells (archaeocytes), at first.
A third point of dispute is whether the nematocysts ar:e formed in situ, or whether the cnidoblasts migrate with them to the region where they are most needed; the fact that in Hydra, for example, there are no interstitial cells in the tentacles, where nematocysts are very abundant, is certainly in favour of the view that the cnidoblasts migrate on to the tentacles from the body, and that like the genital cells the cnidoblasts are wandering cells.
Ge, Genital glands.
Free in a mature condition as the so-called " genital swimming bells," comparable to the Globiceps of Pennaria.
The next chamber, the urodaeum, is small, and receives in its dorso-lateral wall the ureters and the genital ducts; above and below this chamber is closed by circular folds, the lower of which, towards the ventral side, passes into the coating of the copulatory organ when such is present.
In male beetles, however, the two pairs of genital processes (paramera) belonging to the ninth abdominal segment are always present, though sometimes reduced.
The morphology of the abdomen, ovipositor and genital armature is dealt with by K.
B, Diagram of the nephridium of Alciope, into which opens the large genital funnel (coelo mostome).
Beddard) the funnels of the pronephridia disappear except in the genital segments, where they seem to be actually converted into the genital funnels.
At the least there is no doubt that the genital funnels are developed precisely where the nephridial funnels formerly existed.
If the genital funnels are not wholly or partly formed out of the nephridial funnels they have replaced them.
In the genital segments of Eudrilus the nephridia are present, but the funnels have not been found though they are obvious in other segments.
Here also the genital funnels have either replaced or been formed out of nephridial funnels.
The more complete replacements, such as the nephridia of the genital segment of Tubifex by a subsequently formed genital duct, may be compared with the succession of the nesonephros to the pronephros in vertebrates, and of the metanephros to the mesonephros in the higher vertebrates..
The genital ducts are limited to one segment (the 8th in Capitella capitata), and there are genital setae on this and the next FIG.
In other forms genital ducts and nephridia coexist in the same segment.
The Oligochaeta contrast with the Polychaeta in the general presence of outgrowths of the septa in the genital segments, which are either close to, or actually involve, the gonads, and into which may also open the funnels of the gonad ducts.
In dextral Gastropods the only structure found on the topographically right side of the rectum is the genital duct.
Represented by the genital duct.
The sexes are distinct, as in all Streptoneura; and genital ducts and accessory glands and pouches are present, as in all Pectinibranchia.
Y, Vesicle on genital duct.
Accessory organs are rarely found on the genital ducts, but occur in Paludina, Cyclostoma, Naticidae, Calyptraeidae, &c. Mandibles usually present.
In the most primitive condition the genital duct is single throughout its length and has a single external aperture; it is therefore said to be monaulic. The hermaphrodite aperture is on the right side near the opening of the pallial cavity, and a ciliated groove conducts the spermatozoa to the penis, which is situated more anteriorly.
The genital duct is now said to be diaulic, as in Valvata, Oncidiopsis, Actaeon, and Lobiger among the Bullomorpha, in the Pleurobranchidae, in the Nudibranchia, except the Doridomorpha and most of the Elysiomorpha, and in the Pulmonata.
The genital duct is now trifurcated or triaulic, a condition which is confined to certain Nudibranchs, viz.
F, The genital pore.
In front of the osphradium is the single genital pore, the aperture of the common or hermaphrodite duct.
The female genital opening usually lies in front of the eighth abdominal segment, the male duct opens on the ninth.
The female genital opening usually lies between the seventh and eighth segments, the male on the ninth.
14) and the genital armature of the male.
The male opening is on the ninth abdominal segment, to which belong the processes that form the claspers or genital armature.
The genital armature of the male is formed to a considerable extent by modifications of the segments themselves.
Terrestrial and usually littoral; genital duct monaulic, the penis being connected with the aperture by an open or closed groove; shell with a prominent spire, the internal partitions often absorbed and the aperture denticulated.
Visceral mass and shell conical; tentacles atrophied; head expanded; genital apertures contiguous; marine animals, with an aquatic pallial cavity containing secondary branchial laminae.
Visceral mass and shell conical; head flattened; pallial cavity aquatic, but without a branchia; genital apertures separated.
Male and female genital apertures open into a common vestibule, except in Vaginulidae and Oncidiidae.
Shell with medium spire, external or partly covered by the mantle; genital aperture below the right posterior tentacle; genital apparatus generally provided with a dart-sac and multifid vesicles.
Shell external, spiral, generally ornamented with ribs; borders of aperture thin and not reflected; radula with square teeth; genital ducts without accessory organs.