HIRUDO. 41 



be uuimal 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. 



Early 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 



F 



