No. 3.] EGG OF ALLOLOBOPHORA FOETIDA. 605 



how much of the difference in the cytoplasmic configuration of 

 photos. 5 and 6 is due to the difference in fixation, the egg 

 of photo. 5 having been killed in corrosive-sublimate and that 

 of photo. 6 in picro-formalin. Photo. 6 represents, however, a 

 little later stage of development of the ^g%. 



Morphological Similarity of the Cone and Male Aster. 



It is impossible to avoid drawing conclusions as to the mor- 

 phological significance of the resemblance between the male 

 aster and transverse sections through the fertilization cone. 



Photo. 3 shows a transverse section of a fertilization cone, 

 near its apex, and a comparison of this with a section through 

 the male aster of photo. 9 will serve to illustrate this point. 

 The rays and the central aggregation of archoplasm are as 

 pronounced in the one as in the other, suggesting that each 

 end of the head of the SDerm — the spine and the middle-piece 

 (see photo. 37) produces on the cytoplasm of the ^^^ a like 

 morphological effect. This would indicate that the spine and 

 the middle-piece are of the same substance, though the iden- 

 tity cannot be complete, as the cytoplasm does not react to the 

 two structures at the same stage of development of the &^g. 

 There are a few investigators who claim to have traced a sub- 

 stance in the spermatid to both spine and middle-piece. The 

 effect produced by the spine is made, however, by a moving 

 object {the sperm entering the Q^^, and we have thus a different- 

 shaped "aster" — a cone-shaped aster. Is it possible that 

 this may have any bearing on the opposing interpretations of 

 various authors, some asserting that the anterior end of the 

 head of the sperm produces the male aster, and others that 

 the posterior end of the head (the middle-piece) produces it.-* 



If we accept the interpretation of those authors who claim 

 to have traced a part of the aster of the spermatid to both 

 spine and middle-piece, may we not regard that part of the 

 spermatozoon (including spine, head, and middle-piece) as an 

 attenuated spindle,^ and expect that each end of this spindle 



^ Foot, " The Centrosomes of the Fertilized Egg of AUolobophora foetida," 

 Biol. Led., Marine Biological Laboratory. Boston, 1S96. 



