KI.ASMdlili.WCIIS. 



107: 



in tlic skill <it' the Miitr;il side, lictwci'ii flic .•iiiiis ami 

 the iirclliral a|icrtiir(', are (■(|iiall\' (uiiiiil diiriiii;' the 

 lircciliiiji-seasoii, it si'ciiis highly prohiihic that Imlh the 

 iitcrygopodia t'miotionate simultaneously. The situalidii 

 of the iiniLiciiilal o|)eiiiiii;' in the iiialcs, relatively to 

 tlu' hase of the iiti'rv;L;(i|)()dia, is such that tlit? seiiieii 

 iiia\' apjiai'ditlv he reeeived almost iiiimediately in the 

 ahove-meiitioued channel on tlie iiterygopodia. 



Tiie ovaries (tit;'. IWS^ it) oceupv the same position 

 as the testes — in the anterior part of the ahdoiiiinal 

 cavitx' the\- are attached hy means of their niesoariiini 

 (jieritoiieal fold) to the spinal column — hut are sepa- 

 rated from their effei'ent (the Mi'illerian) ducts, which 

 unite hefore them, under the crsoiihagus and just he- 

 liiiid file diaphra.iiin, in a curve, at the middle of wiiicli 

 thev lia\e their common openin.ii' (7). 'l"o this ojieniny 

 the egii's thrown off by the ovaries ;ire conducted hy 

 a current produced by the ciliary motion of the investinsi- 

 cells of the serous tissue lining the interjacent organs. 

 The said curi'cnt may be observed even shortly aftei- 

 the death of the fish by opening the belly, i-emoving 

 or lifting aside the liver, and strewing finely powdered 

 charcoal on the parts. The oviducts (^Miillerian ducts) 

 heiid backwards, one on each side, a,nd are i-acli fur- 

 iiisheil with two dilatations. The anterior (o) of these 

 is glandular, its walls l)eing traversed by ramified ducts 

 that secrete a nidamental substance to envelop tlie eggs; 

 while the posterior ir) is a uterine pouch within which 

 the impregnated ova eitlier undergo the earliest stages 

 of their de\elopment, or remain until the young are 

 fully develo|ied and capable of free motion. In the 

 latter case, when only the right ovary as a rule is 

 functional, the glandular dilatation of the oviducts is 

 little de\-eloped. but the uterus all the more so, its 

 walls being lined with vascular folds or even with a, 

 jildfi'iila iitrihid, into whicli the vitelline sac of the 

 embryo is fitted by means of wai'fy placental grt)Wths 

 (cotyledons), an arrangement that would lie fully ana- 

 logous to the viviparous development of the mammals, 

 it' the yolk sac were replaced by the fcetal fnembraues 

 of the latter. The o\iducts open either into the com- 

 mon cloaca (.S-, .s), on each side of the urethral aper- 



ture (/), or, as mentioned above, at special orifices in 

 the skin. 



TIh; primeval type of the Elasmobranchs has rami- 

 fied in two essentially different directions of evolution, 

 on the one hand I0 the liaJdcepliaJl, on the other to 

 the I'liif/iost(imi. 



Fig 



i-ntraf 



30.^. Fcinnfe 



rail II 



r.f a SliaA. After Owii.N. 



all, tiif ippi-11 and laid back; b, sections of Uie slioulder- 

 •dk' and pelvis; c. licari in its pericardium; /(, hindmost part of 



■ recluin and tlie ascending glandula relrounalis; n, riglit ovary; 

 nidamental dilatation of tlic left oviduct {(jlandida nidamentalis); 

 ciinimon aperture of tlie twii oviducts; at its bottom the orifice of 



■ rinlit oviduct (to the left in the figure); r, uterine division of 

 i left oviduct (the right oviduct lies unopened to the left of the 

 ore); ^', posterior mouths of the two oviducts; t, urethral papilla, 



the tiji I'f which a bristle is inserted into the urethra. On each 

 (■ (if Ihis brisUir may be seen an abdominal pore (the month of a 

 peritoneal canal). 



