3g HIRUDO. 
always obtain the most favourable and interesting inspection of them by 
supplying the favourite prey. 
The pond leech breeds in the end of May or the beginning of June, 
and sometimes afterwards. I do not know that it is equally prolific as 
the preceding subject, the complanata; but their mode of propagation. 
bears a narrow resemblance to each other. 
An irregular cluster of ova is first seen indefinitely through the thin 
skin of the under surface, far down the animal, and rather towards the 
sucker. These daily grow more distinct, appear whiter and spherical, 
and may be enumerated as nine, or in greater number. But they are 
not external. Such was the aspect of a prolific specimen on the 15th of 
August.—Plate IV. fig. 23. 
The breeding season may be earlier or later. On June 25, many of 
this species were taken from a small pond in Heriot Row garden, in the 
centre of Edinburgh, where they dwell in vast profusion. At that time 
all the young were hatched. Like those of the Hirudo complanata, not 
one was free from young ones. 
The Hirudo bin-oculata and complanata dwell together in lakes, where 
they may be found at almost every season, but the preferable period for 
observation is generally between the beginning of April and the begin- 
ning of September. 
Prats IV. 
Fic. 17. Hirudo stagnalis ; bin-oculata—the two-eyed leech, adult, back. 
18. Belly of the same. ‘ 
19. Head and eyes enlarged. 
20. Margin enlarged. 
21. Larva whereon the Hirudo bin-oculata preys. 
22. Fly from the same. 
93. Prolific Hirudo bin-oculata, under surface, shewing a cluster of 
spawn. 
§ 9. Hinupo tessettata—The Chequered Leech.—Plate IV. fig. 24. 
I have been much perplexed in endeavouring to identify this ani- 
mal with the Hirudo tessellata, or Chequered Leech, of the Linnzxan sys- 
