[ 331 ] 
XVIII. Description of an Infusory Animalcule allied to the Genus Notommata of 
Ehrenberg, hitherto undescrihed. By John Dalrymple, FAi.C S. 
Communicated hy Thomas Bell, Sec. K.S. 
Received December 3, 1848, — Read February 15 and 22, 1849. 
The animalcule I propose to describe in the present memoir bears so close a f 
resemblance to Notommata Syrinx of Ehrenberg, that were there not special dif- 
ferences in its internal anatomy, such as I believe could not have been overlooked i 
by that great observer, one might almost believe it to be the same animal. 
The character of the genus is thus given by the Professor in the great folio of j 
1838: — “Animal ex Hydatinaeorum familia, ocello unico occipitali, pede hisulco, 
caudam furcatam referente ; et organo rotatorio, simpliciter ciliato, instructum.” 
These characteristics are mostly taken from its external organs ; but we find, on 
reference to the description of the animal, that it possesses an intestinal tube termi- 
nating in a cloaca or anal orifice, which appears from the plates to be situated at the i 
point where the foot or forcipated tail emerges. The grand structural difference, 
then, to be remarked in the animalcule that forms the subject of the following pages, 
is that there exists no intestine, and therefore no anal orifice, nor any tail or forci- j 
pated extremity. This want of intestine removes it into a lower position, as regards 
animal life, and I would therefore refer it to a subgenus of Notommata, if it be even 
entitled to a place so high in the scale of Infusoria. 
In shape it resembles a flask or bell-flower (corpore campanulato) (Plate XXXIII. 
fig. 1), narrower towards the head and expanded below, of such extreme transparency j 
as to permit all the internal organs to be clearly visible, even to the contents of the jj 
stomach. 
’ I 
It moves slowly and equably, describing, while feeding, narrow circles in the 
water, so as seldom to be far out of the field of an half-inch object-glass ; but when i 
disturbed it will go off in a direct line until it again becomes quiet, or resumes its j 
former slow circular motion. It is visible to the unassisted eye as a minute semi- ' 
transparent spot, and is readily drawn into a glass tube when it is desired to select 
one for examination. Its average length is rather less than half a line, and at its ! 
I broadest part about the fifth of a line in breadth. ['j 
1 In order to convey a correct idea of its anatomy, it will be desirable to describe, {i 
I first, its general appearance and the grouping of the organs, and subsequently to j| 
j take the latter under the heads of the assimilative and reproductive functions. 
It has already been said that in shape this animalcule resembles a bell-flower, or 
I Iti 
