801 



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 majority 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 

 cavity and brought in contact with the air, without the intervention 

 of any true vascular system. 



The beautiful transparency of the animal, and the facility with 

 which the development of the ovum may be traced through all its 

 stages, induces the author to believe it to be well-suited to the in- 

 quiries of the embryologist and of those who devote themselves to 

 the study of the metamorphosis of cell into tissue. 



This animalcule has hitherto been discovered only in a few situa- 

 tions (in Norfolk near Norwich, and in Warwickshire near Coven- 

 try), but it is believed, from the very general dispersion of Infusoria, 

 that it may be more extensively met with, especially in the months 

 of June, July, August and beginning of September. 



The author concludes by expressing his belief that re-examina- 

 tion of the whole order of Rot'ifera is necessary to determine the 

 disposition of the sexes, and to assign them their proper situation in 

 the scale of animated beings. 



