ON CTEXOPIIORES OF THE NEIGHBOURHOOD OF MISAKI. 465 



in making distinction between B. cucumis and B. ovata. According to 

 that view, the branches of meridional canals in the latter species should 

 show communications not only among themselves ' but also with the 

 pharyngeal canal ; whereas, in the former such communications should 

 be altogether lacking. MORTENSEN (191 2, p. 83) alone has* stood 

 against this distinction and has maintained that the character in ques- 

 tion is too variable to rely on and that the two " species " only represent 

 two phases of one and the same species. In the specimens of B. cucumis 

 examined by me, as already described, the lateral branches of meri- 

 dional canals do show a small number of anastomosis among themselves 

 and a few communications with pharyngeal canal. Thus, it is clear 

 that the distinction set up by CHUN can not be held up, indicating 

 that MORTENSE\ is probably right in his opinion. Possibly a point of 

 difference between the two forms referred to consists in the size of 

 e gg s - One morning in the beginning of April, 1918, some individuals 

 of B. cucumis, kept alive in a glass jar at Misaki, were found to have 

 laid eggs. These measured 0.4-O.5 mm. in diameter. Agassiz should 

 have given 0.5-0.6 mm. for the size of eggs of the same species (called 

 by him Idya roseola) of the coast of North America (known to me 

 through Chun, 1880, p. 100). Now the eg^s of B. .ovata, according 

 to YatsU (1912, p. 2) should have a diameter of i-i.2mm. CHUN 

 (1880, p. 100) also has mentioned that the largest ova of that species 

 measured 1.2 mm. in diameter. It must then be said that the egg of 

 B. cucumis, in comparison with that of B. ovata, is half as small or 

 even smaller. 



7. JSeroë campana, n. sp. (Pl. VII, figs. 6, 6 a). 



The body is mitre-shaped, and distinctly compressed, the ratio of 

 the three main axes being on the average approximately 10:7:2. 

 The apex is rather acute ; the polar plates are exposed. The mouth 

 is large, being almost as wide as the body itself, and is without lip- 

 like projections. The distance between subtentacular ribs is greater 



