436 BULLETIN OF THE 



In a subsequent note Fol ('77*') gives the results of recent studies on 

 Asterias glacialis. When the ovule comes into the sea-water the germi- 

 native vesicle shrivels and in some way melts in the vitellus; its contents 

 do not escape, as Van Beneden thought. The germinative spot also loses 

 its sharp contour, becomes pale, often changes form, continues to dimin- 

 ish, and finally dissolves. Then there remain in the yolk only two ill- 

 defined spots, one where the vesicle was located, the other, of ovoid form, 

 approaches the surface. The use of reagents discloses the existence of 

 a double star, which Fol names amphiaster. In its neutral plane this 

 amphiaster often presents bodies of an irregular form which he con- 

 siders as the remnant of the membrane of the germinative vesicle. This 

 is, I believe, the first time Fol records his observation of anything 

 answering to an equatorial nuclear disk.* The remnant of the dot is 

 still visible at some distance from this " amphiaster de rebut," but the 

 author " dares not affirm that no fragment of the germinative dot can 

 enter into the composition of this amphiaster." He afterwards, how- 

 ever, asserts that the female pronucleus has no genetic connection with the 

 nucleolus of the ovule. Fol thinks this first stellate figure {amphiaster) is 

 not yet that which gives rise to the " corpuscules de rebut," but that it 

 divides within the yolk in such a manner that its peripheral star alone 

 gives rise to the amphiaster which is to be expelled. Thus, it is evident 

 according to his description, that there must at one time be at least three 

 stellate figures in the yolk. May he not have mistaken the star of a 

 male pronucleus for one of these three % At least I see no other explana- 

 tion of this statement, for it is quite improbable that any such division 

 as he indicates really takes place in the first amphiaster. 



The internal half of the " amphiaster de rebut " doubles, and the sec- 

 ond globule is formed like the first ; the internal half of this amphiaster 

 changes into a small spot, and becomes a female pronucleus, which 

 migrates toward, but does not reach, the centre of the yolk. These 

 changes are all effected in the same manner, whether fecundation 

 has preceded or not ; if fecundation does not now follow, the e^g 

 gradually decomposes. It was never seen to develop parthenogenet- 

 ically. 



0. Hertwig ('77) arrives at important conclusions from studies com- 

 municated in his second paper on " Bildung, Befruchtung und Theilung 

 des thierischen Eies." The observations were made on eggs of Hiru- 

 dinea and Rana. To the investigation of the former Hertwig was led 

 by the researches of BUtschli, and undertook their study with the pur- 



* Consult in this connection pp. 429, 480. 



