EARLY DEVELOPMENT OF LACEETA MURALTS. 



139 



the blastopore — a supposition which simplifies our ideas as to 

 the orisin of the vertebrate anus in o;eneral. 



Four Transverse Sections through the Hinder End of a Young 

 Embryo of Lacerta muralis (Balfour). 



Sections a and b pass through the whole embryo, while c and d only pass through 

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

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

 j)r. Primitive streak, hg. Hind gut. hy. Hypoblast, jop. Body cavity. 

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

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

 blastic wall of allantois. 



The development of the kidney has been described by 

 Braun.l 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 einbeimischen Reptilien," 'Arb. aus 

 d. Zoolog. Inst. z. Wurzburg,' Bd. iv, 1878. 



