12 Mr. T. Brightwell on Hirudo geometra, 



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 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 longi- 

 tudinal lines upon the posterior disc, and the four eyes in the 

 anterior disc or sucker being clearly visible. They were very 

 active and vigorous, and exceedingly beautiful little animals. 



One of the young leeches being placed in a small cup of 

 water with a tadpole, instantly fixed itself to the edge of the 

 tadpole's tail, and remained so for some hours ; but several 

 tadpoles being placed in the vessel where the young leeches 

 were, they had all disappeared on the following morning, the 

 tadpoles having probably devoured them. The adult leeches 

 all became faint and died, a few days after they had deposited 

 their eggs. 



These leeches were rarely, if ever, observed to move in the 

 geometrical manner which is described by Linnaeus and 

 others, and from which character the trivial name geometra 

 w r as given to them. Our species all moved in the same manner 

 as the common medicinal leech, and often swam about in the 

 undulating manner of that species. Both the young and the 

 old ones also, frequently, after attaching themselves firmly by 

 the posterior disc only, assumed a rigid appearance, and flung 

 their bodies about as if eagerly seeking some object to fix 

 themselves to, which they did, if any object presented itself, 

 in a moment, and were very difficult to detach. 



Cuvier (or rather Latreille), ' Regne Animal/ vol. v. p. 215, 

 describes the genus Hcemocharis as never swimming ; but if 

 our species be of this genus, this must be incorrect. M. de 

 Blainville seems of opinion that the Hirudo cephalotes of Ca- 

 rena is of this genus ; but this species is not only described as 

 never swimming, but also as viviparous ; characters which will 

 not agree with our species, and from which those in Cuvier and 

 other authors may probably have been taken. 



The figure given of H. geometra in the 6 Encyclopedie Me- 

 thodique/ pi. 51. fig. 12 — 19, which professes to be copied 

 from Rosel, differs much from our species both in the form of 

 the discs or suckers, the situation of the eyes, and the mark- 

 ings. 



We add a few general observations on the freshwater leeches 

 occurring in our neighbourhood, Hcemopsis sanguisorba (Sav.), 

 the common horse-leech. This species is common in our 

 ponds and ditches. We have not been able to determine 



