HIRUDO. 35 



cylindrical ; and although hatched in twelve or fourteen days after produc- 

 tion of the capsule, they remain long attached to the body of the parent. 



The whole brood of fig. 12 consisted of about one hundred young, all 

 which had forsaken the parent in forty-three days after the capsule was 

 produced, though some returned temporarily. They feed very soon, as 

 may be discovered from the contents of the interanea. Figs. 7 and 16, 

 enlarged. 



The young frequently assemble in numerous clusters on the side of 

 their vessel after having quited the parent, and in a short time abandon 

 it, each departing to provide for itself. 



These animals have a tendency to dwell in society, especially towards 

 the close of autumn. If a number be then introduced into a vessel, with 

 one of the valves of some of the testacea reversed, all will crowd under 

 it for shelter. 



They are generally very inactive, and will remain entire days mo- 

 tionless among the mud. 



This animal is an excellent guide to some obscurities in the history 

 of the leech. Its history affords the following conclusions : 



1. The Hirudo complanata is dispersed in the greatest profusion in 

 Scotland. 



2. It appears in much variety of size, colour, and general aspect ; 

 sometimes uniformly dull, sometimes speckled, sometimes with a margin 

 formed of rectangular compartments. 



3. It feeds on different animal and vegetable substances, but its 

 natural prey is the Helix peregra. 



4. It produces several capsules invested by a transparent integument, 

 and the young, after production, remain attached to the under surface of 

 the body. 



5. Embryos, distributed in regular numbers, become visible in the 

 capsules at a very early period. 



6. The embryos attain maturity in twelve or fourteen days, and 

 then issue from an aperture in the side of the capsule. But after quit- 

 ing it, they remain for some time attached to the body of the parent. 



7. A single adult may produce one hundred young. 



