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HANDBOOK OF INVERTEBRATE ZOOLOGY. 



the second region it passes into this receptacle, where it 

 remains until it is transferred to the body of the female. 



3. The spermatophore. The seminal receptacle usually 

 contains a spermatophore ; but as this is gradually com- 

 pleted in this cavity, perfectly mature spermatophores are 

 the exception rather than the rule. The arrangement of 

 the parts of the spermatophore varies somewhat in differ- 

 ent species, but the following four structures are always 

 present : the sheath^ the discharging bodies, the sperma- 

 tozoa, and the cement. 



Fig. 124. — Diagrammatic view 

 of the left side of the first ab- 

 dominal somite of a male speci- 

 men of Cyclops tenuicornis, more 

 highly magnified, to show the 

 ripe spermatophore in the termi- 

 nal region of the vas deferens. 

 (After Graber, Taf. xxv., Fig, 3). 

 vd. The enlarged terminal por- 

 tion of spennatophore receptacle 

 of the left vas deferens, sp. Sper- 

 matophore. h. Lid-like plate 

 which covers the external genital orifice at the lower edge of the posterior 

 end of the first abdominal somite, a. Wall of vas deferens, h. A mass 

 of cement inside the cavity of the duct. c. Cavity of the duct. d. Sper- 

 matophore sac. e. Spermatozoa, filling the anterior half of spermato- 

 phore. /. Discharging bodies filling the posterior end. g. Cement body 

 and anterior end. 



(i.) The sheath, or spermatophore sac (Fig. 124, d) is a 

 delicate, transparent, oval pouch, which is secreted around 

 the spermatozoa in the second chamber of the vas deferens. 

 The sheath is not quite complete, since its inner or ante- 

 rior end is open. 



(ii.) The discharging bodies (Fig. 124,/) form a trans- 

 parent mass, which, in some species, fills the posterior 

 closed end of the sac, as shown in the fiijure, but in other 



