W. F. R. WELDON, 



this group of Craniata, the anus is in the position of a part of 

 the blastopore — a supposition which simplifies our ideas as to 

 the origin of the vertebrate anus in general. 



me 



FODR TaANSVEHSE SECTIONS THKOTJGII THE HiNDER EnD OJ? A YOUNG 



Embryo OF Lacerta muralis (Balfour). 



Sections A and b pass llirough the whole embryo, while c and Douly pass through 

 the allantois, which at this stage projects backwards into the section of 

 the body cavity behind the primitive streak, ne. Neurenteiic canal. 

 pr. Primitive streak, hg. Hind gut. liy. Hypoblast, fp. Body cavity. 

 am. Amnion, se. Serous envelope (outer limb of amnion fold not yet 

 separated from the inner limb or true amnion), ul. Allantois. me. Meso- 

 blastic wall of allantois. 



The development of the kidney has been described by 

 Braun.^ My observations lead me, however, to believe that 

 his account of the mode of origin of the segmental tubules 

 and of the Wolffian duct is erroneous. 



' Braun, " Das Urogenitalsystem der einheimischen Reptilien," ' Arb. aus 

 d. Zoolog. Inst. z. Wiirzburg,' Ed. iv, 1878. 



