Instances of the female taking care of her progeny are extremely scarce in fishes. At present only two examples are known, that of the Siluroid genus _Aspredo_, and of _Solenostoma_. In the former, during the time of propagation, the integuments of the lower side of the flat trunk of the female assume a soft and spongy texture. After having deposited the eggs, the female attaches them to, and presses them into, the spongy integument, by merely lying over them. She carries them on her belly, as the Surinam Toad (_Pipa_) carries her ova on the back. When the eggs are hatched the excrescence on the skin disappears, and the abdomen becomes as smooth as before. In _Solenostoma_ the inner side of the long and broad ventral fins coalesces with the integuments of the body, a large pouch being formed for the reception of the eggs. There is a peculiar provision for the retention of the eggs in the sac, and probably for the attachment of the embryo. The inner walls of the sac are lined with long filaments, arranged in series along the ventral rays, and more numerous and longer at the base of the rays than in the middle of their length, behind which they disappear entirely. They are also more developed in examples in which eggs are deposited in the sac than in those which have the sac empty. The filaments most developed have a length of half an inch, and are beset with mamilliform appendages. A slightly undulated canal runs along the interior of the filament. [Illustration: Fig. 73.--Solenostoma cyanopterum ♂ (Indian Ocean).] [Illustration: Fig. 74.--Pouch with ova, formed by the ventral fins of _Solenostoma_. Lower aspect; the edges of the fins have been pushed aside to allow of a view of the inside of the pouch. (Natural size.)] The _Testicles_ of the _Teleosteans_ are always paired, and occupy the same position as the ovaries. Their size varies extraordinarily at the different seasons of the year. Vasa deferentia are constant. In the males of viviparous Teleosteans the urogenital papilla is frequently enlarged, and clearly serves as an intromittent organ. In _Clinus despicillatus_ the vas deferens widens within the abdomen into a cavity occupied by a complex network of loose fasciculi, rising from the mucous membrane. The cavity can be compressed by a special powerful muscle, the accumulated semen being thus expelled with considerable force through the narrow aperture of the penis. In many Cyprinodonts the vas deferens runs along the anterior anal rays, which may be thickened, and prolonged into a long slender organ.