EGG OF ALLOLOBOPHORA FOETID A. 53 



accounts of the development of the spermatozoa where part of 

 the archoplasmic mass in the daughter cells of the spermato- 

 cytes, second order, forms the spine of the spermatozoon, as 

 well as its middle-piece, may we not regard the head (including 

 the spine and the middle-piece) as an attenuated spindle ? And 

 may we not expect each end of the spindle to produce an 

 effect upon the cytoplasm similar to the phenomena at each 

 end of the spindle in the cytoplasm of the spermatocytes ? 

 Would not such a phenomenon produced by a moving body 

 cause a structure like the fertilization cone ? It seems to 

 produce the effect for only a definite time, possibly during the 

 fusing of the substance of one pole (the spine) with the egg 

 cytoplasm; for, finally, the head moves out of the area of the 

 cone, leaving it behind. 



This suggestion of a possible explanation is obviously with- 

 out value unless we find a fertilization cone and a sperm attrac- 

 tion sphere in all eggs where the spermatozoon has a spine and 

 a middle-piece ; for example, in the spermatozoa of Axolotl 

 and Allolobophora foetida we have the spine and middle-piece, 

 and in the egg of both these forms we have the fertilization 

 cone and the sperm attraction sphere. In Myzostoma we have 

 neither spine nor middle-piece, and we have neither fertilization 

 cone nor sperm attraction sphere. 



The fact that the attraction sphere does not appear until the 

 middle-piece enters the egg has served to justify the assertion 

 that the centrosome of the sperm attraction sphere is of the sub- 

 stance of which the middle-piece is formed. (The fertilization 

 cone does not appear until the head of the spermatozoon enters 

 the egg, but we are not tempted to say that the head breaks 

 up and forms the cone, for the simple reason that the head 

 remains intact.) 



The centrosomes of Allolobophora foetida (as they appear to 

 me) furnish a strong support for the view of Dr. Watase" and 

 others as to the strictly cytoplasmic origin of the centrosome. 

 I am not aware that Dr. Watase has definitely stated that the 

 sperm attraction sphere is of cytoplasmic origin, but his paper 

 on the "Homology of the Centrosome " certainly implies it. In 

 the egg of Allolobophora foetida, however (Fig. 4), these little 



