HIRUDO. 4] 
be animal and vegetable substances, possibly the inmates of the Testacea. 
I once thought some portions of the Veronica beccabunga in decay had 
been consumed, and at another, that a different leaf, the only substance 
accessible, had been also consumed. Yet the fact was not corroborated. 
Neither have any experiments with the Testacea proved satisfactory, 
chiefly, however, because they may not have been sufficiently made. It is 
only on discovering errors that we may hope to correct them. Yet 
the naturalist is very often, and very unexpectedly, disappointed. The 
food in the viscera has always seemed dark. 
These animals are frequently in motion. I had one which could 
not be said ever to rest. It traversed its prison incessantly, as long as 
in my possession. During progression the two extremities are approxi- 
mated, to enable the creature to take its step, wherein it resembles cer- 
tain caterpillars. The body then rises in great convexity above the 
surface. 
Being an animal rarely disseminated in Scotland, I have never had 
the good fortune to find specimens so early in the season as to expose 
immature ova. Perhaps they propagate at an early age, probably by ova 
borne in a transparent capsule, round the surface of the belly, or affixed 
to it, and that the embryos bursting thence in segments in the same 
way, affix themselves to the surface of the skin. This habit seems pecu- 
liar to the young of the flattened leeches, the complanata, stagnalis, and 
tessellata, or in other two of which we have yet to treat. 
Here the observer is very liable to delusion in computing the young 
from a single parent in any of three species here named. Nor can he 
fix it with any certainty, without a previous enumeration of the capsules 
pertaining to each. 
The young do not adhere permanently to the same adult, for they 
shift their position. Therefore no uniformity is seen in their number. 
Karly in July I observed at least 150 young adhering to the belly 
of a specimen, which appeared very careful of them,—folding its body 
longitudinally as if for their protection, while it crawled along. The 
brood attached to another still remained late in September. 
When departing, the young animals cluster on the sides of their 
FE 
