HOMOEONEMA ALBA. 143 



The general form of the bell is shown, in side view, in the photograph 

 (PI. 3, fig. 2). The central portion of the gelatinous disc is thick and 

 rounded, the marginal zone thinner. The specimens are all rather flatter, and 

 have a shallower bell cavity than in Vanhoffen's figure (: 02'', taf 9, fig. 5); 

 but since this figure was taken from a preserved specimen (he had only one 

 specimen), and since the outline varies in different specimens in the present 

 collection, it is best not to lay much stress on this difference. 



Tentacles. — These show the same differentiation into proximal and distal 

 regions, as well as the same differentiation in size, as do those of Halicreas 

 jjapillosum; the radial ones are much stouter and longer than those be- 

 tween the canals. Most of the tentacles are broken short off, as is 

 usual in this family. There are from ten to thirteen tentacles per octant 

 (PI. 33, fig. 11), this being about the same number that Vanhoffen (: 02'') 

 has recorded ; and even in the smallest specimen (5.5 mm. in diameter) 

 there are twelve tentacles in the only octant in which counting was possi- 

 ble. The number of tentacles is thus only about one half as great as in 

 Halicreas papillosum. This appears to be a fairly constant difference, 

 and, since the full number is so early attained, may well be accorded 

 specific value. 



Sense organs. — These (PI. 33, fig. 6) closely resemble the otocysts o^ Hali- 

 creas papillosum. I have not been able to determine certainly whether or 

 not they contain otoliths. Browne, who has observed the sense organs in 

 H. 2)latygonon, merely says that " they are external, fairly large, and have a 

 sliort stalk" (: 06, p. 175). The greatest number that I have counted 

 in any octant is three. 



Gastr avascular system. — The stomach is broad and flat (PI. 3, fig. i). The 

 mouth is usually wide open, but in one large specimen, 20 mm. in diameter, 

 it was tightly closed, and easily separable into proximal and distal (lip) 

 regions. Maas (: 06'', p. 10) considers the conformation of the gastric cavity 

 a good distinction between different species of this genus ; but inasmuch 

 as different specimens of H. alba show so much diversity, I doubt whether 

 this chai-acter is of any greater taxonomic importance in this family than 

 it is in the Aequorldae. The radial canals are broad (PI. 3, fig. l), though 

 narrower than in Halicreas papillosum (PI. 3, fig. 3). 



Gonads. — These (PI. 3, figs. 1, 3) are proximal, though not actually 

 continuous with the central gastric cavity. They vary in position in differ- 

 ent specimens, being either closer to or farther from the stomach. It is this 



