78 SUMMA.RY OF CURRENT RESEARCHES RELATDTQ TO 



which are often of great delicacy, are frequently arranged with re- 

 markable symmetry; by some authors they seem to have been 

 mistaken for nerves, (ix.) The female organs exhibit little matter 

 for histological inquiry ; the whole yolk-mass is limited externally by 

 a thin structureless membrane, and contains but a small number of 

 large nuclei. They are unpaired except in the Ptilodineae and in 

 Seison, but it is not yet possible to say whether the duplicity is a 

 primitive or an acquired condition; future inquiries will have to 

 settle whether the mass which produces the summer eggs is morpho- 

 logically different from that which gives rise to the winter ova ; the 

 author is inclined to believe that it is not so. (x.) Males; of the 

 seventy-four genera as yet included in the system of the Rotatoria, 

 there are but twenty-four — Floscularia, Seison, Lacinularia, Conochilus, 

 Triarthra, Polyarthra, Notommata, Syncliseta, EospJiora, Diglena, 

 Hydatina, Monocerca, Monostyla, Golurus, Salpinx, Euchlanis, 

 Metopidia, Brachionus, Apodoides, Anursea, Apsilus, Ascomorpha, 

 AsplancJina, and Hertwigia — in which the males are as yet known. 

 As is well known, the males are of simpler organization than the 

 females. With regard to the method of copulation, the author finds 

 that in Eotifers, as in some Planarians, the penis bores through the 

 body-wall of the female at any point, and is not inserted into the 

 cloaca; under suitable conditions one female may be fertilized by 

 several males. The females of Hydatina were observed to live for 

 about fourteen days, but the male could not be kept alive for more 

 than three at the most ; the former reach their definite size in about 

 three days, and they then begin to lay their eggs. The common 

 view that males are especially common in spring and autumn is 

 erroneous, for they are just as common in the middle of August as in 

 April or October ; the source of error is to be found in the comparative 

 rarity of males. 



In conclusion. Dr. Plate has some observations on the stem-form 

 of the Rotatoria ; it is clear that sexual dimorphism is an acquired 

 character. The " Archirotator " had a cylindrical body, narrower 

 behind, a ventral mouth and dorsal anus, and an aboral tuft of cilia ; 

 the wheel apparatus consisted of two ciliated circlets ; the fore-gut 

 had a chitinous masticatory apparatus, and the whole tract was lined 

 by ciliated epithelium ; into its hinder portion opened two unbranched 

 excretory canals, and the genital ducts. The nervous system con- 

 sisted of a dorsal central ganglion, which gave off several anterior 

 and two postero-lateral nerves. As to their systematic position, the 

 Rotifers appear to be of the same stock as the Annelids, but they 

 differ from the Trochophore in wanting a ciliated groove, the hinder 

 circlet of cilia opens into the fore-gut, the aboral tuft does not cor- 

 respond to the " perianal " circlet, and the brains are not homologous. 



Desiccation of Rotifers. — Mr. H. Davis at a recent meeting of 

 the Quekett Microscopical Club, exhibited some strips of note paper 

 on which were several groups of dried Philodines (P. roseola), looking 

 like clear red spots. These had been sent to Mr. Davis by the 

 Rev. E. T. HoUoway, of Clehanger, who had thus succeeded in ob- 

 taining specimens of these dried rotifers quite free from sand or dirt 



