ORGANS OF GENERATION. 



419 



Fig. 204. 



Structure of the Testes m Clupea Alosa. 



this arrangement we have, therefore, the simplest 

 form of the isolated ovaria of Reptiles, Birds, 

 and Mammalia, in all of which the ova escape 

 from the surface of the ovary, not from its 

 interior; and in the orifice through which the 

 eggs are ultimately expelled from the abdomen 

 we see the first rudiment of a Fallopian tube. 

 In the Lamprey this orifice is prolonged into 

 a short canal, and in Rays and Sharks assumes 

 the form of an oviduct with which we shall 

 afterwards see the Fallopian tubes of Mammals 

 are identical; for whatever the complication 

 which it afterwards assumes, the oviduct or 

 Fallopian tube (for the two are the same in 

 function) only receives the ova after their escape 

 into the cavity of the abdomen to facilitate 

 their ultimate expulsion. In Kays and Sharks 

 the oviduct is double, commencing, however, 

 by a fimbriated aperture common to both, 

 which receives the eggs from the ovaria ; each 

 oviduct is at first narrow and membranous, 

 having its lining membrane longitudinally 

 plicated, but before its termination the walls 

 suddenly increase in thickness, developing in 

 their interior a large gland destined to furnish 

 the horny covering which invests the eggs of 

 these creatures. Beyond the gland the oviduct 

 expands into a capacious bag, which communi- 

 cates with the cloaca. 



In this class of fishes the testis, like the 

 ovary, is not hollow. In the Eel and Lamprey 

 the secretion of the testis escapes from the 

 external surface of the organ into the abdomi- 

 nal cavity, whence, like the eggs in the females 

 of the same tribes, it is expelled through a 

 simple orifice provided for its egress. In these 

 creatures the testis and ovarium are so entirely 

 similar that they have been confounded by 

 authors, the secreting granules in the one sex 

 and the ova in the other being both disposed 



in regular laminae, and only differing inas- 

 much as the testicular granules are smaller 

 than the mature ova. 



The structure of the testis in Rays and 

 Sharks is peculiar, these animals being appa- 

 rently provided with both the kinds of testis 

 above described. Each testicle consists of two 

 portions quite detached from each other; the 

 one is formed of an aggregation of globular 

 masses as large as peas, from which no excre- 

 tory duct has been found to issue ; the other is 

 made up of convoluted canals, which, gradually 

 uniting together, terminate in a capacious tube. 

 The tuberculated mass has been described as 

 the testis, while the convoluted tubes of the 

 other portion were regarded as an epididymus, 

 whence the vas deferens took its origin. There 

 is, however, no communication between the 

 granular part and that whence the vas deferens 

 issues ; it is, therefore, probable that the former 

 is analogous to the solid testis of the Eel and 

 Lamprey, pouring its secretion into the abdo- 

 minal cavity, whence it is emitted through the 

 apertures well known to communicate in these 

 creatures between the peritoneal bag and the 

 exterior, while the latter is identical with the 

 usual form of the testis in osseous fishes. 



TheBatrachian Reptiles in their mode of gene- 

 ration, as well in so many other points of their 

 economy, form the transition from the branchi- 

 ferous to the pulmonary forms of theVertebrata, 

 and hence the study of their sexual organs is ex- 

 ceedingly interesting. The ovaria of these ani- 

 mals in their entire organization resemble those 

 of the Lamprey. Their size, however, is much in- 

 ferior, and the whole organ exhibits a more con- 

 centrated arrangement. The vascular membrane 

 which forms each ovary is arranged in large 

 folds on the sides of the spine, and the ova 

 are deposited in great numbers between the 

 lamellae of which it consists. The oviducts 

 are long and tortuous, each commencing by a 

 fimbriated aperture which is found to be situated 

 at the side of the pericardium, and so bound 

 down in that position by its peritoneal attach- 

 ments that when the interval which separates this 

 point from the ovaria is considered, it is difficult 

 to conceive how the ova, when dislodged from 

 the nidus in which they were formed, can be 

 brought into the oviduct ; the only supposition, 

 in fact, which will account for it is, that the 

 eggs break loose into the abdominal cavity and 

 thus make their way to the extremities of the 

 oviducts. Before terminating in the cloaca 

 the oviducts expand into capacious recepta- 

 cles, in which the ova are collected prior to 

 their expulsion, and glued together by a glairy 

 secretion into masses which distend the whole 

 of the abdomen. 



The ovaria of the Salamanders resemble 

 those of the frog, as do the oviducts, but the 

 membranous sacs which retain the ova are less 

 considerable than in the Anourous Batrachia : 

 the same observations apply to the perenni- 

 branchiate orders. 



The structure of the testis in frogs is almost 

 the same as that of the same organ in the 

 cuttle-fish. If the investing tunic be removed, 

 the whole substance of the organ appears com- 

 posed of globules; but if these are gently sepa- 



