158 



pearance towards the south. It is not impossible, that in 

 their migration they crossed the Isthmus to the continent of 

 South America and founded the race to which the South 

 American skulls belong, which resemble so closely those 

 found in the Ohio mounds. At an intervening point, the 

 Natchez Indians present the same characteristic structure, 

 and were possibly derived from the same stock. 



Mr. Desor gave an account, illustrated with drawings on 

 the blackboard, of the embryonic development of Campa- 

 nularia. 



He stated that he had recently had an opportunity of observ- 

 ing Meduisa3, derived from the Campanularia. This mode of re- 

 production seems to take place earlier than the propagation by ova. 

 The young Medusae were found this year, about the wharves 

 of Boston, as early as the month of March. 1 have ascertained, 

 says M. Desor, that the cross-bands, which are to be seen on the 

 middle of the disc, and which Van Beneden considers as muscles, 

 are four accessory gastric channels, answering to the four similar 

 channels which are so distinctly seen in the Oceania. Those 

 swellings, likevvise, which are to be seen at the origin of the said 

 channels, and which Van Beneden thinks are probably nervous 

 ganglia, are nothing but expansions of the membrane surround- 

 ing the central cavity ; so that all inferences which have been 

 drawn from these statements of M. Van Beneden, as to the 

 presence of nerves in the embryonic state of Polyps, must be 

 abandoned as unfounded. 



M. Desor did not succeed in keeping these young Medusae, 

 the offspring of Campanularia, for more than two or three days 

 alive, and could not therefore study their further growth and 

 development. It has Leen supposed that they might be the 

 young state of Stomobrachium, (the little bell-shaped Medusa, 

 so common at this season about the wharves of Boston) ; but 

 this view, although probable in some respects, is not yet sub- 

 stantiated by any direct observation. 



The observations of M. Desor, whilst confirming in the main 

 the results of his friend M. Loven, have led him to elucidate 

 some points which had remained doubtful. The eggs in their 

 early state are collected in bags attached to the gastric channe 



