No. 3.J EGG OF ALLOLOBOPHORA FOETIDA. 607 



two are shown in photo. 14). We are unable at present to 

 homologize these divisions of the sperm head with the chromo- 

 somes of the egg, not having seen the requisite number. 



If the archoplasm shown at the periphery of this sphere is 

 comparable to Boveri's archoplasm in ascaris, it certainly is not 

 brought in by the sperm, as claimed by several authors for the 

 ascaris ^%g, for here we see the spermatozoon still intact. 



Photo. 13 shows part of the head of the sperm and the 

 entire middle-piece, at about the same stage as that of photo. 

 12, though the magnification is somewhat greater (950). 

 Without more data we hesitate to interpret the two tiny 

 filaments at the posterior end of the middle-piece. One of 

 them may be the proximal end of the tail of the spermato- 

 zoon, or they may both represent the splitting of the proximal 

 part of the tail and its fusing with the cytoplasm of the q.^%. 

 This egg was killed in 2 per cent osmic in 70° alcohol, and it 

 is interesting to compare its cytoplasmic structure with that of 

 photo. 12, in which case the Q.g% was killed in corrosive-sublimate. 



In photo. 14 we have the same stage of development of 

 both sperm and middle-piece. 



In photo. 15 we have transverse sections of two middle- 

 pieces within the aster, and it is scarcely necessary to call 

 attention to their resemblance to a dividing centrosome. The 

 heads of the two spermatozoa are in the adjacent sections. 

 They are contracted rods such as those shown in photos. 16, 

 17, and 18. 



Photo. 16 shows the head of the spermatozoon separated 

 from the middle-piece and contracted into a relatively thick 

 short rod — the middle-piece has (apparently) contracted some- 

 what, and we interpret the filament to the right of the middle- 

 piece as a part of the tail of the spermatozoon. 



In the preparation represented by photo. 17 there is a middle- 

 piece distinctly seen within the sphere ; but it has been oblit- 

 erated by too dark printing in the reproduction, over-printing 

 producing the same results as over-staining. 



In photo. 18 the middle-piece is by no means in the center 

 of the sphere ; but the spherical form of the latter remains 

 intact. If the middle-piece does more than stimulate the ^gg 



