490 BULLETIN OF THE 



brane is accurate, the polar globules ought ahvays to be found outside 

 the membrane in all cases of normal fecundation ; they are, on the con- 

 trary, applied to the vitellus so that they are difficult of observation, 



FoL ('77^) responds to Giard by saying that in the sea-urchins of the 

 Mediterranean which he has studied there does not exist the " cone 

 d' attraction " which in the egg of Asterias is formed in front of the most 

 advanced spermatozoon ; not a single hyaline protuberance appears on 

 the mature egg of these sea-urchins before fecundation. 



The concurrent evidence of 0. Hertwig's and his own studies shows 

 that the polar globules are promptly detached from the ovule, not being 

 retained by any membrane, and are lost in the ovary. Fol finds very 

 small and pale corpuscles lodged inside the outer of the two vitelline 

 membranes which exist in the sea-urchin. There are usually more than 

 two, and as the globules described by Giard appear to correspond with 

 these, he concludes that this author has not observed the true polar 

 globules. Instead of traversing the supposed vitelline membrane by way 

 of diffusion, as Giard thinks, the body of the spermatozoon penetrates, 

 as such, the vitellus, a fact still demonstrable in his prejDarations. 



Fol's ('77^) communication to the Swiss Society of Natural Sciences 

 in August contains, beside what has already been given, some points 

 which are not previously dwelt upon. In the starfishes there is only 

 one vitelline membrane formed, but in the sea-urchins a second mem- 

 brane is formed beneath the first, although it is not detached from 

 the surface of the yolk until the moment of the first segmentation. 

 In the third of the experiments here recounted, the eggs of the sea- 

 urchin were fecundated by mixing them in sea-water with very dilute 

 spermatic fluid, and then at once removed by a pipette to 2% acetic 

 acid, followed successively by osmic acid and Beale's carmine. All 

 these eggs have at one point of their surface a membrane raised up 

 in the form of a watch-glass bulging in the middle and continuous at its 

 margin with the limiting membrane of the yolk. At the centre of the 

 region covered by this membrane the body of a spermatozoon is im- 

 planted in the surface of the yolk by its point. It lies in the direction 

 of the radius of the egg, and has a cue. In eggs hardened a little 

 later the body of the spermatozoon, recognizable by its shape and the 

 color imparted by reagents, is sunk completely into the yolk so that itb 

 blunt end is " flush " with the surface. In place of the cue is a vesi- 

 cle attached to the spermatozoon on the one hand and to the vitelline 

 membrane on the other. The latter is now elevated from the yolk on 

 all sides. A comparison with living eggs and those hardened simply in 



