288 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Japan and Borneo. But, further, it seems to me quite 

 il logical to use the known facts of distribution of a 

 group as characters of species. It is quite absurd to 

 suppose that two animals in all respects exactly alike in 

 structure and form must be distinct species solely because 

 they occur in different parts of the world. 



In the present collection of Acraniates from Ceylon 

 there were no less than 58 specimens of B. belcheri, by 

 far the largest number ever collected at one time. 

 Having so large a collection on my hands I have thought 

 it well to make a detailed comparison of this species and 

 B. nakagawce, and this comparison certainly supports the 

 opinion that these two forms are specifically identical. 

 The data of B. nakagawce are taken from Dr. Nakagawa's 

 excellent tables in his notes on this form. 1 



Size.— The average size of B. nahagaicce was found by 

 Xakagawa to be 35*74 mm. ; this is the average of 119 

 specimens, the longest of which was 54 mm., and the 

 smallest 25 mm. In B. belcheri from Ceylon, the average 

 length of 58 specimens was 41*72 mm., the greatest length 

 being 56 mm. and the smallest 2(> mm. Thus in size 

 they agree very closely indeed. 



Time of spawning. Xakagawa found that the spawn- 

 ing time of B. nakagawce was about June and July. I 

 found that the Ceylon species spawned about March and 

 April, that is, rather earlier than the Japanese form. 

 This is just what one might expect from the spawning 

 time in the tropical seas being earlier than in more 

 temperate ones. 



Oral cirri. The total number agrees closely. 41 in 

 />. nakagawce and 36-41 in H belcheri. 



Myotomes. -The total number of myotomes in H. 

 nakagawce varied between 62-66, the average being 64, 



1 An not. Zool. Jap. Vol. i., part 4. 



