﻿April, 1857.] 



ELLIOTT SOCIETY. 



187 



of them appears to be connected with a slight enlargement of the 

 marginal cord. They differ from the bulbs of the great tentacula 

 by their smaller size, their comparative want of color, and their 

 want of the small lateral tentacula described above. The latter 

 are found on the bulbs of the great tentacula in course of devel- 

 opment before the lash has appeared. 



This genus has a general resemblance to Eucope thaitmantioides, 

 Gegenb., but differs by the presence of the lateral cirrhi to the 

 bulbs of the tentacula. 



The larva is not known. The only observations 1 have made 

 which may have any connection with the development, are the 

 following: — Among a great number of specimens taken at various 

 times during a summer, and nearly all of the same size, we find 

 three different forms of the sexual organ similar to those upon 

 which Gegenbaur separated as distinct species, hisEucope thauman- 

 tioides and E. affinis. In one of these I find the sexual organ a 

 small fusiform gland, situated somewhat nearer to the digestive 

 cavity than to the margin. Two of the glands in fig. 2, PL 11, 

 are somewhat in this condition. The second is that represented 

 fig. 3, on the same plate, [t is oval in form and contains a distinct 

 oval sinus of the radiate tubes. The third form has the sexual 

 organ much elongated and containing a large oblong sinus of the 

 tube. Such was the condition of the organ in fig. 1. Now, so 

 far as my observations yet extend, I have not been able to dis- 

 cover any other constant differences between these forms than 

 those of the sexual organs, and I incline, for the present at least, 

 to look upon the latter not as Gegenbaur has done, as indicating 

 distinct species, but merely as different stages in the growth of the 

 sexual organs in maturing specimens. The case of Nemopsis Gib- 

 besii gives us a remarkable instance of the various appearances 

 which the sexual organ may assume, and leaving the point to 

 further research, I shall give a name in this paper to but a single 

 species. 



EUCHEILOTA VENTRICULARIS. nov. spec. 

 PI. 11, Ff. 1-3; and PI. 12, Ff. 1-2. 



The form is nearly that of a segment of a sphere less than the 

 hemisphere. This is the case while the animal is in full activity 

 and swimming in search of food, but when irritated or drooping, 

 there is a sensible shortening of the diameter of the tentacular 

 circle, imparting a more hemispherical outline. In some speci- 



