258 REPORT — 1851. 



during the whole day. When the leeches separated, a white filmy substance 

 was detached from the parts where they had been united, which in one case 

 had the appearance of eggs, but from subsequent observation it was found to 

 be a film in which the eggs were enveloped. Within twenty-four hours after 

 the union took place, eggs were deposited and were found firmly attached to 

 the sides of the glass vessel. By an experiment made with a pair which were 

 kept separate for that purpose, twelve eggs were found to proceed from two 

 individuals. These eggs were semitransparent, of a reddish brown colour, 

 oblong-oval, with one end truncated ; they were covered with a white filmy 

 web-like secretion, and had longitudinal elevated ridges on the sides. The 

 shells of the eggs were found, on dissection, to be extremely hard. On the 

 thirtieth day after the eggs were deposited the first young leech made its 

 appearance. Each egg produced only one leech ; this was ascertained by 

 detaching an egg and keeping it in a glass by itself, when one leech only 

 proceeded from it. The young leeches were of the size of a small thread, 

 about one-third of an inch long, and appeared perfectly formed ; the brown 

 annular markings of the body, the longitudinal lines upon the posterior disc, 

 and the four eyes in the anterior disc or sucker being clearly visible." 



Mr. Brightwell remarks with reference to the Horse-leech, HcBinopis San- 

 guisorba (Sav.), which is common in our ponds and ditches, "that it is pro- 

 bably oviparous. We have found its young, in an early stage, in the same 

 places as the adult, but never adhering to the parent." He further states 

 with regard to the medicinal leech, " that a dealer in Norwich keeps a stock 

 of about 50,000 in two large tanks of water, floored with soft clay, in which the 

 leeches burrow. On examining these tanks we found many capsules or ova de- 

 posits of the leech, which the owner, ignorant of their nature, stated to be at 

 times very numerous, but which he had neglected and generally destroyed." 



Of another species of leech (Nephelis vulgaris, Sav.), he states, " This 

 species abounds in all our fresh waters, and the brown capsules containing 

 the ova may be constantly found on the underside of the leaves of water- 

 plants among the ova of the freshwater helices. We have kept several spe- 

 cies through the summer, and the following are our notes as to the deposit of 

 the ova and the development of the young. On the 2nd of June II. vulgaris 

 deposited one capsule containing ova ; on the 5th another ; on the 10th an- 

 other ; and on the 15th two more, each of them containing from seven to ten 

 eggs. On the 22nd the young appeared in the capsule deposited on the 2nd, 

 and on the 13th of July they emerged from the capsule, and in six weeks 

 were fully developed and left the capsule. Examining the young of this 

 species with a power of about sixty linear, we detected a Cypris and four 

 specimens of a common rotiferous animalcule in its stomach, one of the Ro- 

 tifera being still alive." 



Of Nephelis tessellata the same observer states, " Miiller says the female is 

 sometimes filled with 300 young ones. The abdomen of our species was, 

 when captured, covered with young, which adhered solely to the posterior 

 disc. We kept this specimen from the 24'th of June to the 28th of August, 

 when it died. The young remained attached to the parent during all this 

 time, and we took some pains to ascertain their exact number, and found 

 they amounted to 143. We never saw the parents or the young ones take 

 any food. The young differed altogether in colour from the parent., the 

 latter being a deep green, the former a light ash-colour. The abdomen of 

 the parent had no pouch, but was much expanded by the adhesion of so 

 numerous a progeny, so much so as to make the form appear very different 

 from the young *." 



* Annals aud Magazine of Natural History, 1841. 



