CEPHALOCHORDA. 



367 



Cephalochorda it would be necessary to establish the correlation between the number of gonads 

 and the total number of somites on a large number of specimens. It would be further 

 necessary to examine the number of somites in a large number at different stages of late 

 larval and early adult life with a view to discovering whether a selective death-rate existed. 

 At the same time it would be interesting to examine the correlation between the number 

 of gonads and the number of somites in the dififerent regions of the animal's body, questions 

 which paucity of data forbids any attempt at answering here. 



TABLE V. 



To sum up briefly what has been written above it may be said (1) that the Cephalo- 

 chorda are with regard to their meristic features a very variable group; (2) that there is reason 

 for doubting that natural selection is now playing much part in modifying them; (3) that 

 genetic selection is probably a factor of considerable importance in modifying the meristic 

 features of the group ; and (4) that the conclusions arrived at here are purely tentative but 

 suggest that an ampler study of the group in this connection might be expected to be of 

 considerable interest. 



