TESTACEA. 43 



These creatures feed both on animal and vegetable substances, and 

 consume the epidermis of each other's shells. 



They deposit great quantities of spawn during summer, in portions 

 of a rude cylindrical form, containing from five to fourteen ova or cap- 

 sules, with a minute embryonic speck in each. — Figs. 3, 4. This, in the 

 natural state, is deposited on leaves, and in confinement on the side of 

 the vessel. Twenty days or more bring the young to maturity, when, 

 on quitting the spawn, they are of the palest brown. Dwells in lakes 

 and ponds. 



Plate IX. 



Fig. 1. Helix per eger, viewed from above. 



2. Under surface. 



3. Spawn. 



4. Spawn. 



Phtsa fontinalis. — Plate IX. Figs. 5-11. 



Length of the shell under half an inch ; volutions four, the first 

 three disproportionately small compared with the fourth ; substance fra- 

 gile, thin, and clear ; animal a Umax ; head distinct, roundish ; sole long 

 and lanceolate, extending considerably beyond the shell ; tentacula two, 

 long and taper, differing considerably from those of the preceding subject ; 

 a black eye immediately in front of each. Three tentacular organs, often 

 difficult to be seen, issue from each side of the sole ; two of them, in 

 front, are shorter than the true tentacula, cylindrical, obtuse, and very 

 flexible. Colour of the shell honey-yellow ; animal paler. 



Like the others, this creature feeds on the equisetum, and other plants 

 of the fresh waters which it inhabits, besides on animal substances. 



Its disposition and habits, however, are very different. Its motion 

 \s swift ; it is lively and active, apparently very contentious, and as if 

 striking with the shell. 



Spawn is produced in July and August, in masses nearly spherical, 

 containing from three to eight ova or capsules, also nearly spherical, with 



