No. 2.] 



THE EMBRYOLOGY OF LIMULUS. 



235 



at either end of the cord. I do not quote my own observations 

 upon the postoral position of the antennulae of Crangon because 

 their accuracy has lately been denied by Weldon^ ('92) and by 

 Herrick ('92), and hence they need confirmation. 



It is evident, I think, from the foregoing resume that we 

 cannot with much confidence compare, somite for somite, the 

 bodies of even the most studied Arthropods, but we may 

 present the following tentative statement, merely remarking 

 that as far as Arachnid and Limulus are concerned, the cor- 

 rectness of our assumption receives confirmation from other 

 sources discussed in this essay. 



It will be noted that this comparison brings the end of the 

 Hexapod thorax, and the hinder margin of the cephalothorax 

 of both the Arachnids and Xiphosures into correspondence. 

 Further, if we insert into the Crustacean line a segment for 



1 Professor Weldon and myself are apparently at variance upon several points 

 with regard to the embryology of Crangon, but the points in dispute cannot be 

 settled except by renewed observation. I would, however, point out that in 

 several places he has attributed to me views which I do not hold and which he 

 would not have obtained had he read my papers carefully or had he availed him- 

 self of his opportunity to talk over the points of difference while his paper was in 

 press. Thus he says (/. c. p. 349) that I claim that the blastopore closes com- 

 pletely. I have ('89, p. 6) repudiated this view. He refers to my " remarkable 

 Fig. 32 .... in which a black dot placed between the optic lobes is called the 

 mouth " as representing my evidence as to the postoral nature of the antennulae. 

 The figure is distinctly stated to be a diagram to illustrate the plane of the sec- 

 tions ; Fig. 1 1 is the one to which he should have referred. I have no desire for 

 controversy, but would respectfully suggest that possibly Weldon's figure (7), 



