Medicinal Leech. 221 



its inferior and inner, and a pair of white spots on its supe- 

 rior outer surface. The colouration also^ it may be observed, 

 of some varieties of the true Medicinal Leech, as also and 

 more markedly of Hirudo troctina, a distinct but closely- 

 allied species, appears to indicate similarly that five smaller 

 or secondary aunuli enter into the composition of the 

 primary segments, by the aggregation of which the middle 

 body is made up. At the anterior part of the body the 

 segmental organs are arranged with less regularity. The 

 segmental organs of one family of marine Annelids, the 

 Capitelleae, are said to resemble those of the Leech in 

 having no inner orifice; and in a few Annelids they may 

 be absent, or represented simply by apertures in the body- 

 walls. 



f. Muscular ductus ejaculatorius of left side, leading from the 



convoluted vesicula seminalis into the base of the flask- 

 shaped intromittent oi'gan. It is by the secretion of the 

 vesicula seminalis that the spermatozoa are agglutinated 

 into a spermatophore. 



g. Club-shaped end of intromittent apparatus, glandular at its 



coecal convex end, and tapering off into the muscular penis 

 below. 



h. Penis, surrounded where it passes out of the integument by 

 a strong sphincter. This orifice is separated by an interval 

 of five secondary annuli from that of the female organs. 



i. Ovary of left side, carried upon one of the short oviducts. 

 The ovary of the other side is seen on the farther side the 

 nerve-cord, underneath which its oviduct passed. 



j. Muscular vagina, in which after sexual congress the sperma- 

 tophore is found. Between the vagina and the two oviducts, 

 a common oviduct intervenes, which takes a tortuous course, 

 and has its coils surrounded by a mass of loose tissue, com- 

 posed of unicellular glands, which are probably the main 

 agents in the secretion of the albumen which envelopes the 

 eggs in the cocoon. The azygos character of the two gene- 

 rative outlets is especially noteworthy. In all other Annelids 

 the generative glands discharge their products by dehiscence 

 into the perivisceral cavity, whence they are taken up by 

 the open mouths of infundibular ducts, as in Ganoid Fishes, 



