326 KING. [Vol. XVII. 



the Qg% where the spermatozoon has entered. I have fre- 

 quently found an extrusion of egg-plasm at this point to form 

 an "entrance cone" (PI. XXX, Fig. 42), as described by Fick 

 and Michaelis, although such a structure is not invariably pres- 

 ent. The spermatozoon enters the Q.gg obliquely, and as soon 

 as its pointed apex has penetrated below the surface, and 

 before the middle-piece is even iji contact with the egg, there is 

 found at its anterior end a small round area containing a finely 

 granular substance which always stains a uniform light pink 

 after the use of the combination stain, and remains uncolored 

 after the use of iron-haematoxylin (PI. XXX, Fig. 43). This 

 area, which is the beginning of the astrosphere, is free from 

 yolk granules and is surrounded by a thick layer of pigment. 



The most careful examination of a large number of eggs in 

 this and the succeeding fertilization stages, preserved and 

 stained in various ways, utterly fails to show any central gran- 

 ule in the astrosphere which might be considered a centriole ; 

 nor is there at any stage a collection of granules or a thicken- 

 ing of the substance of the astrosphere that could be called a 

 centrosome. 



That the astrosphere is called into existence by the presence 

 of the spermatozoon in the &%%, there can be no doubt ; but I 

 have not been able to determine whether it is formed from a 

 substance brought in by the head of the spermatozoon, whether 

 it is an accumulation of a specific substance of the &gg, the 

 "archoplasm" of Boveri, or whether it is a condensed portion 

 of the general cytoplasm as believed by Eismond ('94), Erlanger 

 ('97), and vora Rath. It certainly cannot come from the swell- 

 ing up of a substance in the middle-piece of the spermato- 

 zoon, as found by Fick to be the case in Axolotl. The 

 appearance of the astrosphere in connection with the sper- 

 matozoon before the formation of the male pronucleus, and its 

 early division into two distinct parts while the female pronu- 

 cleus is still near the periphery of the ^gg, invalidate for this 

 egg the explanation of the origin of the astrosphere advanced 

 by Carnoy and Lebrun ('97), namely, that each pronucleus con- 

 tains a centrosome which migrates into the cytoplasm when 

 the two pronuclei come together, and so influences it that two 



