54 TESTACEA. 



organ resembling a feather projects from above towards the lip of the 

 shell, or a little beyond it, of which the best view is obtained by the 

 animal endeavouring to regain a horizontal position, when the shell is 

 reversed. One, or even several tentacular -like organs, as long, or longer 

 than the true tentacula are alike active, sometimes appear farther down. 

 Colour of the shell various shades of wood-brown, yellow or chesnut 

 brown. Animal bluish grey. Feeds on the JEyuiselmn. 



This is a very vivacious active animal. It dwells in lakes and tran- 

 quil streams, from which it may be sometimes withdrawn in considerable 

 numbers. One of its favourite haunts is between the lower folds of the 

 yellow Iris. 



There being either different species or varieties exhibiting very slight 

 distinctions or peculiarities among them, these general observations are 

 meant to apply to the whole in common. 



The branchial organ is not uniformly shewn. Some shells appear 

 smooth and shining, and there was considerable discrepancies in size and 

 colour. 



This creature spawns profusely during August, in small globules of 

 a greenish or yellowish hue, and not half a line in diameter. The same 

 individual spawns more than once. Each globule contains from about 

 six to twenty embryonic specks. Fig. 18 ; the same enlarged, fig. 19 ; 

 other spawn enlarged, fig. 20. 



The great season of spawning is the middle of August, when globules 

 are seen on plants and stones. These are frequently so transparent as 

 almost to elude observation when entire. But it is often produced on the 

 sides of glass vessels, and is then very convenient, as affording good op- 

 portunities for inspection. 



The spawn is contained in a hardish membraneous capsule, which 

 gapes in discharging its contents, and afterwards appears empty, fig. 21. 

 While full it is not seen so distinctly. 



Some peculiarities attended the embryonic evolution. 



The specimen, fig. 16, produced three globules of spawn on the 3d 

 and 4th August, one of which is represented, fig. 20. On the 17th these 



