W. H. Leigh-Sharpe 
9 
The circumstances under which fertilization may be effected have 
already been discussed. 
The characters which indicate that Ganymedes cratere is a stationary 
parasite are: (1) its peculiar attachment to anal papilla of host by 
means of an enormously developed anterior sucker; (2) the weak 
development of longitudinal muscle layer; (3) the shallowness of the 
posterior sucker; (4) the rarity of the leech. 
Fig. 6. Ganymedes cratere. General scheme of the reproductive system, p. penis; 
6 bursa; d.e. ductus ejaculatorii; m.g. male genital aperture; f.g. female genital 
aperture; P. the first pair of testes; v.e.^, v.e.-, v.e.^ the first three pairs of vasa 
efferentia; v.d. vasa deferentia; od. oviduct; ov. ovary. 
Calliobdella lophii and Ganymedes cratere resemble each other in the 
following main characters : 
(1) The great development of owe sucker; (2) the general agreement 
as to segmentation; (3) the similar positions of genital apertures and 
anus; (4) the presence of respiratory vesicles; (5) the coiled vas deferens 
in clitellum; (6) the absence of eyes; (7) the typical (or “complete”) 
abdominal segment of six annuli; (8) the absence of blackish-brown 
star-shaped pigment cells; (9) nerve cord within the ventral sinus; 
(10) similar divisions of the coelomic sinuses; (11) both species are 
probably stationary parasites upon a single host. 
