DEVELOPMENT OF THE CTENOPHOEA. 109 



in external conditions, but is of no importance in tlie present 

 inquiry. 



In his account of the changes undergone by Beroe in the course 

 of its development, Chun is not quite in accordance with some of 

 the results at which my own observations led me to arrive. After 

 the four endodermal sacs have been differentiated, their lacuna?, 

 according to Chun, flow together two by two into a common 

 cavity ; and the place of the original four sacs is thus taken by 

 two, from which all the vessels originate by a process of out- 

 bulging. My own observations, on the other hand (see above, 

 p. 91), lead me to conclude that the two endodermal sacs which 

 lie one on each of the broad sides of the compressed stomach, 

 become directly transformed into the two deep-lying or gastric 

 vessels, while the remaining two sacs, by lateral extension and 

 dichotomous division, give origin to the rest of the vascular 

 system. 



In connexion with the embryology of the Ctenophora, Chun 

 records an observation of considerable interest. He noticed, after 

 a succession of very hot days, that the greater number of larv« of 

 Eucharis muUiconiis collected by the towing-net had their sub- 

 ventral meridional vessels changed into pouch-like swellings of a 

 whitish colour. Many of these larvae had plainly only just left 

 the egg, while all were in a very early stage of development. In 

 none of the more advanced larvse could he find a trace of this 

 peculiar condition of the vessels. 



The microscope showed that the whitish pouches were filled 

 with sexual products — that they represented, in fact, herma- 

 phrodite glands, in which occurred, along with sperm-masses, eggs 

 in various stages of development. Chun further proved that the 

 eggs thus produced by the sexually mature laiwa of Eucharis 

 were capable of passing through a development entirely similar 

 to that of the eggs of the adult Ctenopliore, from which these 

 differed only in being about half their size ; and he concludes 

 that the young larva of Eucharis not only becomes sexually 

 mature, but that it gives birth to a brood which again assumes 

 the form of the larva. Several questions, however, connected 

 with this phenomenon still remain unsolved ; and the ultimate 

 destiny of the sexually mature larva, and of the brood to which 

 this gives birth, must await further observations for its deter- 

 mination. 



