258 



COMPARATIVE ANATOMY 



CHAP, 



penis. The bursa is a spacious sac-like invagination of the posterior 

 end of the body which can be evaginated in copulation. Three pairs 



of cement glands are generally con- 

 nected with the male apparatus, their 

 ducts entering the terminal division of 

 the vas deferens (ductus ejaculatorius). 

 Annulata. The Hirudinea are 

 hermaphrodite. Their male genital 

 apparatus (Fig. 173) has the following 

 general structure. Several testes lie 

 in pairs segmentally arranged in the 

 middle region of the body, generally 

 between the consecutive lateral diver- 

 ticula of the mid-gut, within the muscu- 

 lar septa separat- 

 ing these diverti- 

 cula the testes 

 thus divide these 

 septa into anterior 

 and posterior lam- 

 ellae. A short effer- 

 ent duct arises 

 from each testis. 

 The ducts of all 

 the consecutive 

 testes of one side 



emerge into a vas 



FIG. 172. Representation, partly dia- d e f erens which 



grammatic, of the organisation of a male Qei 



Echinorhynchus. r, Proboscis with barbed runs through the 



hooks, protruded ; rm, retractor muscles of -whole length of 



the proboscis; rs, proboscis sheath; rn, ,, fpqfl - p i p rpo -irm 



proboscis nerves ; g, cerebral ganglion ; re, tne testicle region, 



retinacula; li, ligament; sn, longitudinal 111 front of the 



nerves; h, testes; vd, vas deferens; *6, most an t er ior tes- 

 vesiculse seminales'; Ted, cement glands ; gg, . , 



common vas deferens ; gag, genital gan- tlS the tWO 



glion ; bs, bursa ; mo, male genital aperture ; deferentia 

 Ih, body cavity ; p, penis ; I, lemnisci. 



FIG. 173. Genital or- 

 gans of Hirudo. p, Penis ; 

 mo, male ; wo, female geni- 

 tal aperture ; ov, ovaries ; 

 h, testicles; vd, vas de- 

 ferens. 



vasa 

 con- 

 verge towards the 



middle line, here to open outwardly by a common aperture, or in some 

 cases by a common unpaired copulatory apparatus (penis). 



The number of testes may in some cases be greatly increased (Nephelis, 

 Lumbricobdella}, and this probably results from the subdivision of each testis into 

 several vesicles. Complications often occur in the last portion of the vasa deferentia. 

 For example, in Hirudo, the vas deferens, before entering the penis through a short 

 terminal passage, forms a tangled coil on each side. Glands are often connected with 

 the penis. The male genital aperture in Hirudo is in the 10th segment, between the 

 30th and 31st rings. 



The female genital apparatus (Fig. 173) lies behind the male 

 aperture, and generally between the vasa deferentia. It consists of 



