604 PHILOSOPHY OF ZOOLOGY. 



subivided as follows: 1. Mouth armed with teeth, Hirudo 

 (H. medicinalis and sanguisorba, are British examples *). 

 '2. Mouth with a proboscis, Glossopora (, (G. complanata, 

 LIN., Trans, vol. ii. tab. xxix. and bioculata, UKES Hist, 

 of Rutherglen, p. 234 are British species). 3. Mouth sim- 

 ple. This includes three genera. Erpobdella, (Br. sp. 

 E. vulgaris, tessulata and lineata). Fisciola (Br. sp. P. 

 geometra). Pontobdella, (Br. sp. P. muricata.) To these 

 may be added Phyllene (of M. OCKEN), and Trochsetia 

 (of M. DUROCHET.) The last of these, however, breathes 

 air, and should probably be placed near the Lumbricus. 



The leeches are oviparous ; but as they greedily devour 

 different species, (when confined), and even the young ones 

 of their own species, and readily vomit them again, when 

 writhing in agony on a table, it is probable that such cir- 

 cumstances, which have frequently presented themselves to 

 us, have given rise to the belief that some of the species 

 are ovoviparous. 



b. Destitute of terminal suckers. This includes two 

 very distinct families. 



1. PLAXARIAD.E. Ventral surface flattened, and capable 

 of acting as a foot. There are two genera: 1. Planar-la, 

 (MULLER) mouth towards the middle, or posterior portion 

 of the ventral surface, in the form of a retractile funnel- 

 shaped proboscis. There is a contiguous pore, which is 



* These species were formerly considered as destitute of eyes ; but the 

 presence of these organs has been recently ascertained by Professor CARENA. 

 See his valuable Monograph of the genus Hirudo, published in the Memoirs 

 of the R. Acad. of Sc. of Turin, vol. xxv. p. 281. The aerating organs are 

 delineated by Sir E. HOME, Phil. Trans. 1815, Tab. xiii. 



t This genus was instituted by Dr JOHNSTON of Bristol, Phil. 1817, 

 p. 329. In the same vol. p. 13., there are some curious observations on the 

 JErppbdeHa vulgaris. 



