46 HIKUDO. 



those with eight, the eye is disposed in two different arrangements, being 

 either marginal, or in four pairs. 



The length of the specimens of this species when quiescent, was from 

 six to more lines ; when extended about fourteen lines. General form 

 not unlike the Medicinal Leech. Form of the head lanceolate or trout- 

 shaped. Eyes two, black, in front. The viscera consist of thirteen pair 

 of transverse sacs, sufficiently conspicuous in some specimens. The body 

 is composed of numerous segments slightly indented. 



The predominant colour is yellow, sometimes very vivid, sometimes 

 dusky ; and there are specimens whose contrasting hues expose four 

 longitudinal rows of beautiful yellow spots, running down the whole 

 back to the sucker, which itself has a marginal circular row. Under the 

 microscope these, so ornamental to the eye, prove to be only irregular 

 transverse short marks. 



Though the general form of the animal while quiescent corresponds 

 with that of the medicinalis, it is not so thick, plump, and heavy as the 

 tessellata, nor alike tremulous. Also some of the young at an early stage 

 appear quite cylindrical. 



Much of the beauty of this animal depends on the colour. Besides 

 the four rows of yellow spots down the whole back, there is a marginal 

 row on each side, which can be see/> from below. Plate V. fig. 1. Hirudo 

 flava, young ; 2, the same, enlarged ; 3, head more enlarged ; 4, another 

 specimen, natural size, back ; 5, the same, enlarged, sucker a ; G, belly 

 of the specimen fig. 4 ; 7, the same, enlarged, sucker a ; 8, head more en- 

 larged, shewing the eyes. 



It has not appeared what is positively the food of the yellow leech. 

 The ponds wherein I have found it abound more with decaying leaves 

 than with anything else which was likely to afford it sustenance, and it 

 always reposes on or under them. 



This species breeds chiefly from May until August, and is a fine 

 example of what, in more important living beings, might be called a 

 marsupial gestation. Hence a great correspondence is shewn with the 

 nature of those with which it has been more associated, as with the bin- 

 oculata and complanata. 



