38 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 tune 

 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. 



PLATE IV. 



FIG. 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. 



23. Prolific Hirudo bin-oculata, under surface, shewing a cluster of 



spawn. 



9. HIRUDO TESSELLATA 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 Linnaean sys- 



