ANATOMY AND METAMORPHOSIS OF CYCLOPS. 



233 



species it forms a layer just inside the sac, over the whole 

 spermatophore. 



If a male with a ripe spermatophore be gently pressed 

 under a cover-glass, the wall of the sac may be ruptured 

 so that the contents may escape as shown in Fig. 125, and 

 the discharging bodies (c) may then be seen to be small, 

 transparent, highly refractive spherules, which soon absorb 

 water, swell, and disappear. When the ripe spermato- 

 phore is transferred from the reproduc- 

 tive organs of the male to the body of 

 the female, as described further on, the 

 contact with the water causes these 

 spherules to swell, and drive the other 

 contents of the spermatophore out of 

 the sac into the seminal receptacle of the 

 female. 



FIG. 125. Contents of a ripe spermatophore of 

 Cyclops tenuicornis, which has been ruptured by 

 pressure. (From Graber, Taf. xxv., Fig. 5.) 



a. Cement, b. Spermatozoa, c. Discharging 

 bodies. 



FIG. 125. 



(iii.) The greater part of the cavity of the sac is filled 

 by the spermatozoa (Figs. 124, c; 125, h ; 126). When 

 forced out by pressure they will be seen to consist of an 

 oval sheath with an inner spiral thread. The spermatozoa 

 of Cyclops are motionless % 



(iv.) The anterior end of the s'ac is usually occupied by 

 an adhesive plug, the cement (Figs. 124, g ; 125, a) ; but 

 in some species the cement occupies the central axis in- 

 stead of the anterior end. 



4. If possible notice the manner in which the spermato- 

 phore is transferred to the vulva of the female, where it is 



