18 HIRUDO. 



On the 13th of August several leeches had been committed to a 

 cylindrical vessel of water, for the purpose of obtaining their capsules. 

 One appeared in four days, which contained five specks. Two of these, 

 however, proved either illusive or abortive ; but three of them, enlarging 

 circularly at first, had become oval in the course of development, as 

 embryos, within a week. Eleven days subsequent to the production of 

 the capsule they extended and contracted ; yet neither external eyes nor 

 internal organs were visible. They were of singular structure, the whole 

 being formed as if by united vesicles or large globules ; all having some 

 rotundity, nothing angular. It could not be determined whether they 

 were hollow. Two of the embryos were nearly equal ; the third, between 

 them, smaller. In a fortnight they occupied nearly the whole capsule ; 

 and in eighteen days from its production very little of it remained free. 

 In twenty days the lower half of the young appeared deeply corrugated, 

 yet no segments were perceptible, neither could circulation of the blood 

 be discovered. Quite a different character distinguished the upper half 

 of the animal, in being perfectly smooth throughout, thus inducing me 

 to conclude the dark portions of the other to be intestinal. The eyes 

 appeared as minute specks across the front of the upper surface. The 

 surface of the skin had a reticulated aspect, and there were slight remains 

 of the vascular structure above described, fig. 14 ; one of the embryos 

 enlarged, fig. 15. No other motion than simple contraction and exten- 

 sion was then sensible. 



Two having attained maturity forsook the capsule thirty clays after 

 it was deposited ; the third, testifying much activity, escaped two days 

 later. 



Thus, in August and September, the eight- eyed leech comes to ma- 

 turity in thirty or thirty-two days after production of the ovum con- 

 taining it. 



The young leeches on exclusion extend to about the third of an inch, 

 and are of pale amber colour, swim actively amidst the element, and 

 adhere by the sucker in the course of the day. 



It is of the deepest interest to the reflecting mind to watch the pro- 

 gressive evolution of matter from the moment the dormant spark of life 



