Desmidiece.'] hyalotheca. 365 



crenate appearance, or a grooved rim at one end, \Yhicli forms a 

 bifid projection on eacli side ; end view circular. — Ralfs. 



1. Hyalotheca dissiliens, Smith. 



Hab. Penzance^ &c., Mr. Ealfs ; North Wales, Mr. 

 Borrer ; Kent, &c., Mr. Jenner ; Essex, Mr. Hassall ; 

 Bandon, Professor Allman ; Ambleside, Mr. Sidebotham ; 

 Bristol, Mr. Broome ; Stoke Hill, Mr. Thwaites ; Aber- 

 deen, Dr. Dickie ; Ayrshire, D. L. 



1 have fixed on this species because I do not suppose 

 that it is uncommon. I have got it in several localities ; in 

 Ayrshire, in particular, it is very abundant, in a little pond 

 near Turf Dyke coal-pit, Stevenston. It is very beautiful 

 when examined with a microscope, or even a good pocket 

 lens. I first knew it under the name of Conferva dissiliens, 

 and in its general appearance it greatly resembles some of 

 the Confervce proper, unbranched. The filaments are of 

 considerable length, and fine as a human hair. Look at 

 one of the filaments : though you see no difference in the 

 two extremities, you would be disposed to say that one end 

 must be the base and the other end the summit — the former 

 the older, and the latter the younger of the two. You are 

 fairly out ; for the two ends are the oldest portions of the 

 filament. At first there were two valves, forming one cell. 



