93 



XVIII. — On tJie Anatomy of Notommata aurita, an Animal of the 

 Class Rotifera. By P. H. Gosse, Esq. 



(Read May 15, 1850). 



The animal which I propose to describe appears to have been seen 

 by only two observers, Miiller and Ehrenberg. The latter quotes in- 

 deed, with a mark of doubt, our own countryman Baker, but I see 

 little reason to identify his description or figure with this species. 

 Miiller, in 1786, described and figured its external form, and named 

 it Vorticella aurita ; and Prof. Ehrenberg, first in the ' Berlin 

 Transactions,' in 1830, and recently in his noble volumes on the 

 Infusoria, has added to our knowledge some of the more con- 

 spicuous organs, and has included it in his genus Notommata. 



The eared Notommata is an inhabitant of our fresh waters, espe- 

 cially those which are still and occupied with aquatic vegetation. I 

 first obtained it from a reservoir in my own garden, about the half- 

 decayed leaves of the common duckweed (Lemna minor). More nu- 

 merously it occurred in water from a pond in the grounds of Samuel 

 Berger, Esq., of Hackney, in which the yellow water-lily grows. 

 But still more abundant I found it in a jar of water obtained last 

 autumn from a pond near Walthamstow, which had stood in my 

 study-window through the winter. In February, I found the sides 

 of the phial swarming with this Notommata, and with a species of 

 Salpina. 



This fine species is about ,Vth of an inch in length, when ex- 

 tended (as at PL XII. fig. A.) ; but its contractions and elongations 

 render it ever varying. Its form viewed dorsally is somewhat cylindri- 

 cal, but it frequently becomes pyriform, by the repletion of the abdomi- 

 nal viscera. Viewed laterally (as at B.), the back is arched, gibbous pos- 

 teriorly, with the head somewhat obliquely truncate, the belly nearly 

 straight. The posterior extremity is produced into a retractile foot, 

 terminating in two pointed toes : tliis, both in function and struc- 

 ture, is certainly analogous to a limb, and must not be mistaken for 



