[UK KI.IAI. MKM1WAM - I MAMMALS. 



231 



which was i ut op.-n in tin- j [.npaia ; - aliantois (0J) 



is attached to the \vry end of the intestinal (anal l.y means of the 

 attenuated stalk-like uiachus. 



Up to this stage the correspondence in the development of the embry- 

 onic memhranes in Mammal^. I'.ii d>. ami Ili-pt iles is clear. But from 

 DOW on the course of development in the Mammalia becomes more 

 :.ial more diveigent, since one portion of tie totbryonic membranes 



Fig. 134. Embryo Log of 25 dayr, extended and Men from in front. Magnified 25 diameter*. 

 After BISCHOFF. 



rf, Intestine ; ds, yolk-sac ; al, allantois, urinary sac ; wn, primitiM- kidiicy ; [, the two lobes of 

 the liver, with the lumen of the oruphalomesenteric vein between them ; ve, ht, anterior and 

 posterior appendages ; h, heart ; m, mouth ; au, eye ; g, olfactory pit. 



enters into closer relations with. th*> MOMM no'/ntn-aur <>/ ih>' uterus, 

 and is thus converted into an organ of nutrition /or tl>* embryo. In 



this inftnner a compensation is provided for the loss of the yolk. 



The interesting adaptations for intra-uU-i inr nutrition they have- 

 been studied especially by the English anatomic Ti I;M i; in a 

 series of profound compaiative-embryolo^ical works pr/>ent very 

 great differences in the separate orders of Mammalia: sometimes 

 they are of a simple kind, at other times they are more com- 



