BREEDING. lvii 



compact, of a circumscribed form, and placed far forwards in the abdominal 

 cavity. The vasa deferentia communicate with the ureters and terminate 

 upon a cloacal generative organ, external to which on either side, and mostly 

 attached to the anal fins, are the claspers.' The female organs are (as in the 

 male) situated far forwards, and remarkable by the modification of the two 

 oviducts, which are not merely distinct from one another, but also from the 

 ureters, which latter terminate upon a prominent urethral clitoris between the 

 outlet of the oviducts. The ova are few, and the ovaries are comparatively 

 smaller than in osseous fishes. Different parts of the oviduct may be 

 functionally modified, being divided by a circular valve, which separates the 

 upper or narrow portion where the gland is placed which secretes the egg 

 purse, while the lower or uterine part is where the embryos' are formed 

 in the viviparous species. The ova are fertilized while still contained within 

 the oviduct, where the ova are delayed, and the young may be either 

 occluded in horny cases or even produced alive. Among cartilaginous 

 fishes of the ganoid order oviducts are present with small ova. 



During the breeding season certain additional developments may occur 

 in some teleostean or bony forms : glands, as in some carps, may appear oh 

 the heads of fishes of either sex, while among the Salruonidas a knob shows 

 itself in the male sex on the extremity of the lower jaw in the salmon 

 and some trout. Likewise in a carp, Rhodeus amarus, found on the continent 

 of Europe, a long oviferous tube appears during the nuptial season, but as 

 in the case of the knob on the jaw of the salmon is subsequently absoi-bed, 

 while as a rule the female fish is larger than the male. 



Considerable differences in the form of the male generative organs are 

 observable among the bony fishes, but at the breeding season, all that are 

 not sterile have a great augmentation in size. This organ, when arrived 

 at seasonable maturity, is commonly known as the " soft roe " or 

 " milt." It is not necessary for fishes to have attained adult size in 

 order to be capable of the reproductive process or the milt to be fully 

 developed, as this may be seen in the par or young of the salmon. 

 Without detailing the different forms in which these organs exist, it will 

 suffice to remark that when vasa deferentia are absent in the males, oviducts 

 are similarly wanting in the females, the parallelism between these organs 

 in the two sexes being, as a rule, very close. When the testis is single so 

 is the ovary. But in some cases, as in the Salmonidce, although vasa 

 deferentia are present in the male there are no ducts in the female. In most 

 osseous fishes the ovaries form two elongated sacs, closed anteriorly, but 

 posteriorly continued into a short and wide oviduct, which terminates behind 

 the vent and mostly before the urethra. The inside of these sacs is more or 

 less lined with the stroma, or a peculiar tissue within which the ova are 

 developed. In those forms in which the ova are hatched before extrusion, 



