488 BULLETIN OF THE 



an attempt made to contribute by special personal studies of the phe- 

 nomena to the solution of the questions considered. 



In a preliminary note on fecundation, Fol ('77'^), beside communicat- 

 ing the substance of what has already been given, defends his conclu- 

 sions from the adverse opinions of Perez and Giard. Giard's view, that a 

 large number of spermatozoa are necessary (by the motion they impart) 

 to fecundation, is refuted, he claims, by his (Fol's) method of artificial 

 fecundation, in which only two or three spermatozoa were allowed for a 

 single egg. The cases of abnormal fecundation prove that in the eggs 

 of this species the existence of a membrane with a micropyle cannot be 

 admitted. If there were a membrane, as Perez and Giard assert, there 

 would have to be numerous micropyles. 



The results communicated by 0. Hertwig ('77") in a preliminary 

 paper will be considered in the review of the ultimate papers (0. Hert- 

 wig 78 and 78") at pages 495 and 509. 



The act of fecundation in Serpula — as was also stated in his previous 

 work on the development of that animal — is, according to Stossich 

 (77, pp. 214, 217), external ; the spermatozoon does not enter into the 

 egg, but remains attached to its surface by means of the head, and not by 

 the tail. The substance of the mature spermatozoon undergoes a process 

 of transformation, by which its molecules are found in motion, which is 

 eventually shared by the material of the egg. The movement develops 

 itself at first in the external layer of the yolk, in the form of a rotary 

 movement of the vitelline granulations, accompanied at the same time 

 by a chemical transformation of the fundamental material, by which new 

 granules are deposited and the material is rendered more opaque. In 

 consequence of these transformations, there is secreted the gas or liquid 

 previously mentioned by Stossich. (See p. 428.) 



The discussions on the nature of fecundation in Echinodermata are 

 further continued in " Comptes rendus," etc., by Fol on one side, and 

 Giard and Perez on the other. The principal points under discussion 

 are : (1.) whether fecundation is effected by the penetration of a 

 spermatozoon ; (2.) whether there exists a vitelline membrane before 

 fecundation ; (3.) the nature of the vitelline protuberances called by Fol 

 " cone d'exsudation " and " cone d'attraction." 



Fol (77^) responds by concluding that the negative results of Perez 

 and Giard are due to their having studied only eggs already fertilized, a 

 possibility he himself has carefully guarded against by the use of his 

 compressorium, wherein one may observe the eggs from the first instant 

 of the mingling of the two sexual products. Only three or four sperma- 



