137 



ity, yet actual congelation of their tissues was fatal to theni. In 

 those cases in which it had been said that fish had been actually 

 frozen and afterwards recovered their activity, he supposed that 

 a low degree of action in the organs of circulation and respira- 

 tion must have been still kept up. 



Mr. Ayres stated that he had received during the winler a 

 Cat-fish in a frozen state, which when thawed was found to be 

 living. He had also had in his possession a species of LinmcEa 

 inclosed in ice without injury. 



Mr. Desor gave an account of his recent investigations 

 upon the development and transformation of the common 

 Jelly-fish of Boston harbor, Aurelia au7'ita, Mlill. as fol- 

 lows : 



It is now ten years since M. Sars first astonished the scientific 

 world by his discovery that the Medusae undergo a series of 

 transformations not less remarkable than those of insects. The 

 brood when first hatched resemble infusoria, being covered with 

 fine ciliae, by means of which they swim about in the water. 

 After some days they become fixed by one extremity, whilst at 

 the opposite extremity those little processes appear, which by 

 degrees are transformed into tentacles. Transverse folds are 

 said to appear next, at regular distances on the body, the grooves 

 between which, gradually deepen, and the folds become serrated 

 on the edge, so that the whole mass takes the appearance of a 

 pine cone. At last the fissures become so deep that the layers 

 between them are united only by a very slender axis, so that they 

 resemble a pile of saucers. At a later stage they disengage 

 themselves from each other, and each division becomes a free 

 Medusa. 



Larva forms of the Medusa have, since their discovery, been 

 observed only in Scotland by Sir John Dalyell, who made them 

 the subject of an elaborate investigation. They had never been 

 noticed on this side of the Atlantic. It was Mr. Desor's good 

 fortune, in visiting in company with Dr. Bowditch one of the 

 wharves of Boston, at the beginning of the present month, to find 

 them attached in great numbers to the logs. They appeared to the 

 naked eye, as small red dots, which might easily be mistaken for 

 very young Aclinicc. 



