HIRUDINEA. ' 631 



longitudinal vas deferens on either side of the body. The two vasa 

 deferentia are either coiled or dilated at their anterior extremities, and 

 unite in the middle line. The Gnathobdellidae have a protrusible muscular 

 penis ; the Rhynchobdellidae a short eversible sac. Attached prostatic 

 glands are present in both cases. The female organs consist of a pair of 

 ovaries, a pair of ducts which unite, and in Gnathobdellidae form a long un- 

 paired portion, or utero-vagina. The ducts of both testes and ovaries 

 develope independently of the glands in Clepsine (Nusbaum). The true 

 ovaries of Hirudo are two solid bodies, inclosed each in a capsule which is 

 a part of the coelome, and into which the two oviducts open. The epi- 

 thelium of the ovarian sac itself produces the ova and yolk-cells of Pontob- 

 della and the egg-strings of Nephelis. The similar strings of Clepsine 

 probably have a similar origin. There is a sexual congress, except perhaps 

 in Clepsine, where it is possible that self-fertilisation occurs \ The sperma- 

 tozoa are inclosed in a spermatophore. The ova are laid together with 

 albumen in a cocoon, which is secreted by the glands of the clitellum 

 (supra), and which is stripped off by the withdrawal of the fore part of the 

 body of the parent. But in Clepsine the ova are united by the secretion of 

 the glands of the ventral surface of the clitellum, and are thus attached in 

 a mass to some foreign object in the water ; the parent broods over the 

 mass, and the young when hatched attach themselves to its body. Nephelis 

 affixes its cocoon to water plants, but the cocoon of Hirudo and Aulostoma 

 is laid in damp earth. Segmentation is unequal. A remarkable meta- 

 morphosis occurs in some instances (Aulostoma, Nephelis}. The larval 

 ectoderm, muscle-layers, nervous-layer (?) of reticulated cells, are thrown off, 

 a new pharynx is formed, and with the exception of the epithelium of the 

 mesenteron, the whole body of the future Leech is derived from paired 

 mesodermal rudiments, two cephalic, and two for the body. There are two 

 pairs of provisional kidneys. The young Leech has a coelome with septa 

 corresponding to the somites. A number of posterior somites fuse to form 

 the sucker. 



The Hirudinea live for the most part in water, fresh or salt ; some, 

 however, are terrestrial, like the widely-spread Land Leeches (Ceylon, the 

 Himalayas, Java, Sumatra, various East Indian Islands, Japan, New South 

 Wales, Queensland, Trinidad, and South Chili), or subterranean forms such 

 as the European Trocheta and the South American Cylicobdella, and Mac- 

 robdella Valdiviana, which is the largest Leech known, and is said to attain 

 a length of two and a-half feet. The majority are parasitic, and suck the 

 blood of animals (Vertebrates, Snails) ; some are carnivorous like Aulo- 

 stoma, Trocheta, Macrobdella. 



1 The somite behind the clitellum in Macrobdella, i. e. the twelfth, bears on its ventral aspect a 

 swollen oblong area, within which open twenty-four gland pores. These glands may possibly sub- 

 serve copulation (Whitman, op. cit. p. 379). 



