408 PROCEEDING.^ OF THE ACADEMY OF [1890. 



equatorial ly round the pyriform yolk-bag, and the other, which is 

 closely adherent to the first-named, has its fibres running at right 

 angles to the latter, and consequently corresponding in direction 

 with the greatest elongation of the yolk-sack. As far as the speaker 

 is aware, nothing similar in the form of an involuntary muscular 

 coat covering the yolk is known in any other embryo fish. 

 Whether its function is to increase the strength of the yolk mem- 

 brane under the peculiar conditions of tension or whether it served 

 to force the contents of the yolk-bag within the abdominal parietes, 

 as happens during the disappearance of the yolk, the speaker did 

 not attempt to decide. 



The statement in Jordan and Gilbert's Synopsis of the Fishes of 

 North Avierica, p. 750 that: "the young of some or all the species 

 (of the Batrachidre) fasten themselves to rocks by means of an ad- 

 hesive ventral disk which soon disaappears," must accordingly be 

 qualified as incorrect so far as it carries the implication that the act 

 of adhesion is a voluntary one on the part of the young fishes them- 

 selves. The researches of the speaker show very conclusively that 

 the adhesion of young toad-fishes is effected in the first place, at the 

 time of oviposition, by a mucous secretion covering the outer surface 

 of the eggs, and this is supplemented at a later period, or after 

 hatching, by the development, through a modification of certain cells 

 at the surfiice of the yolk-sack, of an adhesive disk, produced by the 

 modification of the substance of the peripheral or free portions of 

 the cells of such an area which adheres to the inside of the egg-mem- 

 brane. The embryo is thus left enchained for a period at the same 

 place where the eggs were originally deposited but in such a way as 

 to be free to respire the surrounding water and to freely vibrate the 

 fins and tail. It is, therefore, clear that the fixation of young toad- 

 fishes is a very complex yjrocess some of the steps of which are 

 effected by the parent at the time of oviposition, while others are 

 effected during the process of the development of the embryo itself, 

 so that it is clear that s^ich a fixation is not voluntary and has noth- 

 ing in common with the voluntary and momentary adhesion, by 

 means of modified fins such as is witnessed in the cases of the Gobie- 

 socidcE and Cyclopteridce. 



November 11. 

 The President, Dr. Joseph Leidy, in the chair. 

 Forty-eight persons present. 



Remarks on Velella. — Prof. Leidy exhibited specimens of Velella 

 mutica, which with many others, where cast on shore at Beach Ha- 

 ven, N. J., in the early part of last August. The living ones were 

 of a deep blue color and ranged from an inch and a half to three 

 inches in the greater breadth. From them there were detached 



