258 PISCES. 



always surrounded by a circle of vessels. The delicate seminal 

 canals proceed from the lobules of the testis, and from them arise 

 nine to ten short, transverse, and parallel vasa ejferentia, that run 

 transversely toward the vas deferens ; the latter is very much con- 

 torted, and continued superiorly into a dense epididymis, which was 

 for a long time taken for a particular gland, its connexion with the 

 testicle having been overlooked owing to its being concealed by a 

 lobulated mass of white and granular fat, deposited upon the plexus 

 of seminal canals, as in the Rays and Squalus canicula. The testi- 

 cles and vasa deferentia frequently lie more close to each other, as in 

 Scymnus, where the large convolutions of the vasa deferentia distinct- 

 ly project above the much elongated cylindrical testes. Inferiorly 

 the efferent ducts expand to form bladders or long sacs that are 

 completely filled with semen. At the end of the cloaca we also find 

 some short tubercles tolerably well developed, and reminding us very 

 much of allied structures in the Tritons ; the semen issues from their 

 conical points, and a circular fold, surrounding them like a prepuce, 

 completes their analogy with the penis. We find also peculiar 

 auxiliary organs, belonging to the external generative apparatus, and 

 consisting of long cartilaginous styliform appendages hanging to the 

 anal fins or pelvic extremities, and channeled by a groove, along 

 which the semen actually escapes from the male, and is probably 

 brought by a kind of copulative act in contact with the female geni- 

 tals. These parts are often seen to be red, turgid, and besmeared 

 with a bloody slime. In their dilated or clavate extremities a num- 

 ber of interarticulated cartilages is recognised ; these, like the whole 

 organ, may be moved by adductor and retractor muscles. 



The testes in Amphioxus consist of small bladders, similar to the 

 ovaries. 



The Spermatozoa exhibit a variety of forms ; those of the Osseous 

 Fishes are rounded and conical, with very long and delicate tails 

 sometimes, as in Cobitis, they have a small appended nodule. In 

 the Plagiostomi they are very generally long and linear, with deli- 

 cate tails ; sometimes they are spirally twisted at the commence- 

 ment, as in the Passerine birds, but run to a finer point, or else 

 they are stiff and straight ; they are also spirally convoluted in the 

 Chimaerae. 



In Fishes, as in Reptiles, we find many viviparous as well as ovi- 

 parous genera. Numerous diversities are visible in the form, size 

 and structure of the ova, but these belong to the developmental 



