380 WHITMAN. [Vol. IV. 



of an effort to press the sperm-case firmly to the surface of 

 attachment, and very Hkely the case was filled with spermatozoa 

 by the same act. After a few moments of steady pressure, — 

 just long enough to allow the sticky secretion to "set," — the 

 leech released its head and slowly drew back, allowing the 

 spermatophore to be gradually pulled out of the two sac-like 

 ends of the vasa dcfereiitia. I saw this operation repeated 

 several times by the same individual at intervals of about thirty 

 minutes. 



Among twenty or thirty spermatophores, I found only one on 

 the ventral surface, and this was near the margin of the body ; 

 the rest were attached to the dorsal side, sometimes between 

 two rings, sometimes in the middle of a ring, without any dis- 

 crimination of place, so far as I could see. 



Although the sperm-case is formed in two distinct sacs, unit- 

 ing in a commiOn pore, its two halves are firmly glued together, 

 as the result of being pulled out through the single pore, while 

 they are still in an adhesive condition. The moment they are 

 set free, they are hardened by the action of the water, and only 

 the small free ends sometimes remain distinct and separate. 



One of the spermatophores first deposited measured 8 mm. in 

 length and i mm. in width. Some of the last obtained meas- 

 ured only 3 mm. or even less. Repetition of the act seemed 

 to exhaust the individual's power of forming spermatophores. 

 Widely as they varied in size, they always showed essentially 

 the same form as that shown in Fig. 4, a and b. 



In the spermatophore we may distinguish (i) a short, con- 

 stricted, basal portion with a single tubular lumen, formed in the 

 median unpaired portion of the male organs ; (2) an elongated 

 body with a double saccular lumen, formed in the enlarged 

 end-portions of the vasa deferentia covnmmia ; and (3) a free 

 end, consisting of two distinct parts, adherent or separate, with 

 lumen closed, or reduced to a narrow line, formed in the ends 

 of the ejaculatory ducts {d) at the point marked w in Fig. 5. 

 The wall of the spermatophore, which is thickest at the base 

 and thinnest in the saccular body, is composed of two well- 

 defined layers : an outer, thin, transparent, finely striated, non- 

 stainable, cuticular-like layer (Fig. 2, d), which appears to fill 

 the angles between the two halves of the case (Fig. 4 b), and 

 to serve as a medium whereby the case is firmly glued to the 



