518 Royal Society. 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAL SOCIETY. 



Feb. 22, IS^Q. — Read a paper, entitled " Description of an Infusory 

 Animalcule allied to the genus Notommata of Ehrenberg, hitherto 

 undescribed*." By John Dalrymple, Esq., F.R.C.S. 



The examination of various specimens of the animalcule described 

 by the author, disclosed the dioecious character of one of the more 

 highly organized of the rotiferous class of Infusoria, hitherto sup- 

 posed to be androgenous. This discovery was first made by obser- 

 ving the difference in the form and development of the embryo 

 while still enclosed in the ovisac of the parent animal. From the 

 extreme transparency of this form of rotifer, it is possible to trace 

 the progressive development of the young from the Grseffian vesicle 

 in the ovary to the period of mature gestation, when the embryo is 

 expelled, the whole machinery of whose organs has been perfected 

 while still within the body of the female. 



Thus, although the young one observed in the ovisac, when nearly 

 ready to be expelled, was in the great maj(»rity of instances a mi- 

 niature portrait of the parent, yet occasionally an embryo was seen 

 of a different aspect, within whose body a vesicle was discovered 

 filled with actively moving spermatozoa. 



A further investigation of the subject brought clear evidence of 

 the functions performed by this male, — its copulation with the young 

 females; but it also displayed the singular fact, that although the 

 organs of reproduction and locomotion were highly developed, there 

 was a total absence of those of assimilation ; in fact, that neither 

 mouth, nor stomach, nor other digestive cavity or glands, were pre- 

 sent in its curious organization. 



In the early part of the paper the author describes the anatomy 

 of the female, which differs from the family of Notommata of Ehren- 

 berg, in the absence of intestine and anal orifice, and forcipated or 

 caudal foot. In every other respect the organization is so similar to 

 that class, that the author believes the proper place for this animal- 

 cule to be in a sub-genus of Notommata. 



In relation to physiology, the author submits a new theory of the 

 mechanism of circulation and respiration in the general group of 

 Rotifers, a subject which is but obscurely treated of by the great 

 German observer, who appears to have believed in the existence of 

 tubular vessels or true vascular system. The author thinks, how- 

 ever, that these functions are performed in a manner more resem- 

 bling that of insects, viz. that the blood is contained in the general 

 cavity of the animal and circulates round the lung, which is here 

 represented by a contractile vesicle that receives and expels the 

 water in which the animalcule lives, and so comes to be in interme- 

 diate relation with the air mixed with the water. The difference 

 therefore between the aeration of the blood of insects and that of this 

 rotifer is rather due to the difference of the media they respectively 

 inhabit, than of design. In both, the blood is contained in a general 



* [A paper on this subject by Mr. J. Brightwell, illustrated with a plate, 

 appeared in the ' Annals ' for September 1818. — Ed. Ann. Nat. Hist.'] 



