334 



transparent. Mr. Bickmore said that this was the second specimen 

 only of this interesting genus that had been taken on our coast ; the 

 first having been found by Messrs. Stimpson and Gill near the same 

 place. 



Mr. F. W. Putnam said that the specimen exhibited seemed to differ 

 slightly from the figures of the European species of the genus; but it 

 would be impossible to decide upon the identity or non-identity of our 

 species with the European until specimens are received from Europe 

 with which to make the comparison. There have been several spe- 

 cies of the genus AjiipMoxus, or Branchiosioma, described : among them 

 is one fi'om the West Indies, described by Sundevall under the name 

 of Branddostoma caribceum. Dr. Peters has considered this identical 

 with the European species. The specimen found by Mr. Bickmore 

 will very likely prove to be the same species as B. caribcEum. Mr. 

 Putnam thought that it was hardly possible for Branchiostoma to be 

 the young of some Myzont, as has been suggested ; as he did not know 

 of any Myzont on our southern coast but the Lancelet. 



Dr. J. Wyman gave an account of the results of his obser- 

 vations on the development of skates, and especially of 

 JRaia hatis. The following changes were noticed : — 



The vitelline duct, during early fcctal life, forms, in connection with 

 the omphalo-niesenteric vessels, an umbilical cord, which, however, soon 

 becomes shortened, so that, during the middle and latter stages, the 

 foetus rests directly upon the yelk. 



The form of the embryo is at first eel-shaped, and then shark-shaped : 

 before reaching its permanent form, the pectoral fins take on the pro- 

 portions of those of Pristis, Rkinobatus, and Sguatina. The dorsal 

 fins are formed on the middle of the tail, but subsequently change 

 their position to the end of it. In the Torpedos, and many other Se- 

 lachians, this change of place does not take place. In recently 

 hatched young of Raia hatis, the tail is still prolonged beyond the dor- 

 sals, as is permanently the case in Uraptera. 



Adult skates have no anal fin : the eaibryos of them, however, have 

 a remarkably large and broad one, until the middle of their foetal life, 

 when it becomes atrophied, and wholly disappears. The branchial fis- 

 sures are originally seven in number : the seventh closes up wholly ; 

 while the 'first is transformed into the spiracle, and is homologous with 

 the Eustachian tube and the outer auditory canal of air-breathing ani- 

 mals. The nosti'ils first appear as simple depressions in the integu- 

 ment, at a distance from the mouth ; and the curious flap between 

 them is the result of the thickening of the intervening skin. This, as 

 Professor Agassiz has pointed out, very closely resembles the intermax- 

 illary bud of the embryos of the higher animals. 



