Till: < F 'HIP MIDIM I 



355 



through disassociation of the cells. In tin- manner there has now 

 11 between epidermis and parietal middle layer a longitudinal 

 canal, which st retches over several segments of the tr"nk and com - 

 in 11 nicalcs w it h the body-cavity by means of sewial sucoeaireope] 

 the pronephric funnels (fig. 194 vn). At one plan- tin- pronephric 

 duct comes close up to the epidern 

 and fuses with it (fig. 198 vg). A\- 

 though an actual opening is never 

 formed here. Mill, supported by this 

 one may e.\pre>s the conjecture 

 that originally the pronephros in Ver- 

 trl nates opened out at a point far 

 forward on the body (VAN \Vuiii:, 

 RUCKERT). 



A short time after its format ion the 

 fundament undergoes in its anterior 

 half a complete dc generation ; the pos- 

 half, on the contrary, is further 

 developed and' enlarges, but remains 

 in connection with the body-cavity by 

 means of a >ingle- funnel only (tig. 194 

 i-it), either brcau>c. as VAN \\'i.ini: AS- 

 :d funnels are fused into 

 u single one, or because, in accordance 

 with the account of RUCKERT, all the 

 funnels except a single one become 

 closed and dt generate. 



In the Amphibia, with which the 

 Bony Fishes exactly agree in this point, 

 the pronephros is established in the 

 most anterior part of the trunk as 

 an organ that is from the beginning 

 hollow (fig. 199). Below the primitive 

 sigments, which have already been 

 dill'erentiaied into muscle-fibres (m), 



there app. ars a groove-like evaluation () of the parietal layer 

 of the peritoneum, which stretches from in front backward 

 several somites. By detaching itself from its parent-tissue at 

 several places, and r< maining in connection with it at others, it is 

 converted into a longitudinal canal, whi-h in liana and Bombinator 

 oommunicatea with the body-cavity by means of three pronephric 



Tig. 193. Cross section through a 

 very young Tadpole of Bombinator 

 in the region of the anterior end of 

 the yolk-sac, .if 



a, Fold of the outer germ- layer that 

 is continued into the dorsal tin ; 

 M*, si'in.-tl o>nl ; ;,i, latoral muscle; 

 a**, outer n -li -l.iv, r <>{ the muscle- 

 phite ; *, iU'-.-<-m-iivm:itii- ivlls ; 6, 

 transition of the \mr\\. 't.il into the 

 i.il iiiiddlo lnyrr; <(, }iri>nephlO6; 

 /, int.->tin.il civity; f, ent> 

 which is rnntiimoiis with tlio mn 

 of yolk-cells ((/);/', ventral coocal 

 liiu-h of the intestine, wliich b- 

 I tho li\er. 



