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[Vol.. I. 



tails of the spermatozoa all turn in one direction, as depicted 

 in Figs. 10, 11. While these changes of the spermatids are 

 in progress, the blastophore itself changes its form from sphe- 

 roid to oblong and sometimes becomes spindle-shaped (Fig. 12). 

 As shown above, the central cells of the original cluster 

 degenerate to form the sperm-blastophore, which appears as a 

 homogeneous substance. It should be here stated that cases 

 have been observed in which several nuclei were scattered 

 through the homogeneous substance of the blastophore, but 

 rarely a complete cell, as shown in Fig. 13. The question 

 arises as to the origin of these nuclei or cells. It seems rea- 



Sp.ph. 



KlG. 12. 



FIG. 13. 



sonable to suppose 

 that they are simply 

 belated portions 

 which have not yet 

 been transformed 

 into the homogene- 

 ous mass. Fig. 7 shows a condition in which only the nuclei 

 remain. At no time during the formation of the blastophore 

 has a proliferation of the central cells been observed. 



The spermatophore becomes slightly modified in passing 

 from the sperm-sac to the spermatheca, as shown in Figs. 12, 

 14, 15. It is to be noticed that the tails of the spermatozoa 

 turn spirally ; this being a secondarily acquired character oc- 

 casioned by its passage through the sperm-duct. Following 

 these changes, the sperm-blastophore becomes more or less 

 spindle-shaped ; it also decreases in size. In the cross-section 

 of a spermatophore a central canal is generally to be seen, as 

 represented in Fig. 15. The blastophores are at first com- 



