REPRODUCTION AND DEVELOPMENT 



105 



by means of spermatophores secreted in the terminal portion of 

 the male duct, the atrium. The only known exception among the 

 Glossiphoniidae is Theromyzon tessulatum in which the atrium can 

 be everted in the form of a low cone which functions as a penis. 

 Typical spermatophores are illustrated in Fig. 55. Although the 



(b) 



Fig. 55. Various spermatophores. (a) from Erpobdella; 

 (b) from Trachelobdella punctata; (c) from Placobdella para- 

 sitica, b.p., basal plate; p.s.y proteolytic substance; 5, sperms; 

 zo, wall of spermatophore. From Grasse, 1959 after Brumpt 

 (a) and (b) and Whitman (c). 



shape varies greatly from one species to another they all consist of 

 a median chamber from which originate two horns. The median 

 chamber may be enlarged at the expense of the horns, or vice versa, 

 and the horns may be widely separated as in Erpobdella or closely 

 bound together as in Glossiphonia. The upper part of a spermato- 

 phore is packed with sperms but the lower one third usually 



