﻿Dec, 1857.] 



ELLIOTT SOCIETY. 



259 



embryos, like those described, and though my observations are 

 not yet sufficiently detailed to enable me to give a full history of 

 the growth of each part, I am yet assured that the following gene- 

 ral statements are true : 



First. That Bolina, in the course of its development, passes 

 through a stage wherein it has the form and the tentacula of 

 Cydippe, as distinguished from Pleurobrachia. 



Second. That at first the four-branched transverse tubes, one 

 on each side of the central chamber about the digestive cavity, 

 have the form of two large quadrangutar sinuses. 



Third. That the peripheral, or ambulacral tubes, or their repre- 

 resentatives, ascend to the sense-capsules before they begin to 

 develop themselves downward towards the mouth. 



Fourth. That the gastric tubes reach the mouth before the 

 superficial tubes. 



Fifth. That the tentacular chambers are at first on a level with 

 the apex of the digestive cavity, and that they afterwards gradu- 

 ally descend, as the animal grows, until they reach their ultimate 

 position one on each side of the mouth. 



Sixth. That the tentacula are atjfirst capable of extending them- 

 selves several times the length of the body, behind the animal, as 

 in Pleurobrachia, but that as they grow they lose this power, by 

 degrees, until, in the fully developed adult, it entirely disappears. 

 However, that it continues, to some extent, even after the large 

 lateral lobes have reached a high degree of development. 



Seventh. That the four narrow ciliated ribbons which hang near 

 the mouth, between the great lobes, two on each side, in the adult, 

 are the last external appendages developed, and do not appear un- 

 til some time after the great lobes are recognizable as such. 



I may add here, that it is probable that but a short time only 

 elapses between the discharge of the ovum and its assumption of 

 the form of figure 1, PI. 14. What changes intervene I have not 

 been able, so far, to discover. 



In a later month, (October 3d) I found in my jars two embryo 

 Ctenophores of a quite different appearance from the young of 

 Bolina. They were more elongate, and broader at the mouth 

 than the latter. Their ambulacra, confined as in the Bolina em- 

 bryos, to the upper portion of the body, were continued almost to 

 the sense-capsule, around which a few of the dendritic yellowish 

 appendages of the superior pole of the body, known in adult Be 

 roes, were already sprouting. Scattered over the outer surface also 



