Development of "Rotifer vulgaris. 133 



of his visual organ or to the circumstance that his specimens 

 of Rotifer were furnished with more rapidly vibrating cilia 

 (i. e. fresher) than mine. 



It is waste of time to dispute about this. All observations 

 in which we must approach the limit of microscopic vision 

 are precarious. Consider only the question as to the general 

 constitution of the striated muscular fibre, as to which the 

 observations of investigators are often diametrically opposed. 

 "Wherever the diffraction phenomena of light come into play 

 microscopic anatomy must put a bridle upon its desire of 

 knowledge. 



I proceed now with the exposition of the anatomical cha- 

 racters of the body of Rotifer. On each side of the chyle- 

 intestine, about the hinder third of the body, are situated the 

 fusiform ovaries. One of them is usually considerably larger 

 than the other ; but each of them is enveloped by a thin 

 transparent membrane, which is drawn out at each end of the 

 organ into a solid cord. The posterior and thicker of these 

 cords passes into the foot and is attached in the vicinity of the 

 contractile vesicle ; the other is longer and more delicate, so 

 that its point of attachment in the anterior part of the body 

 can with difficulty be determined. It is not to be denied that 

 this mode of attachment of the ovaries has a striking simi- 

 larity to those which occur in the still undeveloped ovaries of 

 the larva? of Chironomus plumosus, Gorethra ) &c. As is well 

 known the above-mentioned Dipterous larvee, shortly before 

 their escape from the egg (frequently also even earlier), already 

 possess, in the last segment but three, on each side a distinctly 

 recognizable, fusiform sexual rudiment, which, indeed, is 

 frequently concealed by the adipose body, but is never wanting 

 in the portion of the body indicated. In Rotifer and the 

 other Rotatoria each ovary consists of a finely granular colour- 

 less substance, in which are imbedded large dark nuclei, sur- 

 rounded by lighter spaces. Leydig has interpreted the nuclei 

 as germinal spots and the light zones around them as germinal 

 vesicles. In the smaller ovaries I count five or six, in the 

 larger ones from twelve to fifteen such structures. Frequently 

 the ovaries seem nearly to disappear ; at least I have observed 

 that in many examples of Rotifer they are scarcely a fourth 

 of their original size. 



In the description of the body-cavity of Rotifer it must 

 also be mentioned that it is seldom quite free from embryos. 

 Usually three are contained in it, one of which is generally 

 pretty far developed, while the other two are only in course of 

 formation. During the movements of the parent-animal the 

 progeny are driven to and fro in the most reckless fashion, 



