OF PERIPATUS CAPENSIS. 909 



the anterior somites of the previous stage, or by the formation 

 of new somites anteriorly to those of the previous stage. 



In the next stage it is obvious that this anterior pair of 

 somites has been converted into the prasoral lobes. 



The anterior of the two openings to which the blastopore 

 gives rise is placed between the second pair of somites ; we 

 shall call it the embryonic mouth. The posterior opening 

 formed from the blastopore is elongated, being dilated in front 

 and continued back as a narrow slit (?) to very near the hind 

 end of the embryo, where it presents a second slight dilatation. 

 The anterior dilatation of the posterior open region of the 

 blastopore we shall call the embryonic anus. 



Lately, but too late to be figured with this memoir, we have 

 been fortunate enough to find an embryo of apparently precisely 

 the same stage as fig. 37. We are able, therefore, to give a few 

 more details about the stage. 



The measurements of this embryo were : 



Length of whole embryo . . . . . i -32 mm. 



Distance from front end of body to front end of mouth '32 



Distance from embryonic mouth to hind end of em- 

 bryonic anus -52 



Distance from hind end of embryonic anus to hind end 



of body "45 



Length of embryonic anus - 2 



part of blastopore behind embryonic anus . '2 



Greatest width of embryo '64 



Stage E. In the next stage (figs. 38 and 39) the flexure 

 of the hind end of the body has considerably increased. The 

 anterior opening of the blastopore, the embryonic mouth, has 

 increased remarkably in size. It is circular, and is placed 

 between the second pair of mesoblastic somites. The anterior 

 dilatation of the posterior opening of the blastopore, the em- 

 bryonic anus, has, like the anterior opening, become much 

 enlarged. It is circular, and is placed on the concavity of the 

 ventral flexure. From its hind end there is continued to the 

 hind end of the body a groove (shewn in fig. 39 as a dotted 

 line), which we take to be the remains of the posterior slit- like 

 part of the posterior opening of the blastopore of the pre- 

 ceding stage. The posterior dilatation has disappeared. The 



