340 Miscellaneous. 



of the second segment, which is elongated in the shape of a neck. 

 At the moment of the falling-off of the epimerite, which is easily 

 observed under the microscope, a broad wound is produced by which 

 granulations of the endocyte make their escape ; but this promptly 

 cicatrizes, and the Gregarine soon no longer exhibits any traces of 

 its first segment — it has passed into the Monocystis stage. 



The development of these two species is thus identical with that 

 of the genus ScJineideria, which we may justly consider as the most 

 perfect type of the Dicystid Gregarines. The only difference con- 

 sists in the fact that the epimerite always remains very simple and 

 rudimentary in Doliocystis, while in Schneideria it attains a certain 

 degree of complication. Moreover it is interesting to note that, in 

 a general way, the epimerites of the marine Gregarines never 

 exhibit so high a degree of differentiation as do those of the majority 

 of the terrestrial forms ; they all belong, at least in the species 

 which I have studied hitherto, to the group of the regular simple 

 epimerites. 



The free stage is succeeded in Doliocystis by encystment and 

 sporulation, which take place normally as in the other Polycystidea. 

 The cysts of Doliocystis 7iereidis, which I have succeeded in culti- 

 vating in spite of their extremely small size, give rise when mature, 

 by means of sim])le rupture, to oval corpusculated spores, measuring 

 7 /x in their long axis by 5 p in their short axis. They exhibit a 

 remarkable thickening of the wall at one of the poles, which is a 

 very important character in my opinion, since it is also common to 

 the spores of the genus Schneideria. 



Thus we see that the Gregarines with a single segment from the 

 digestive tract of marine worms exhibit the same mode of develop- 

 ment and the same form of spores as do the typical Dicystidea ; it 

 is therefore in this group that they must in future be placed, and it 

 is necessary to distinguish them henceforth from Monocystis proper, 

 the development of which is entirely different, and which, more- 

 over, inhabits almost exclusively the general body-cavity. 



While retaining the generic name of Monocystis for these latter 

 forms, I propose to unite the former, that is to say the pseudo- 

 Monocystis of the digestive tract of worms, under the common 

 generic name of Doliocystis ; as regards their specific name, this will 

 be very well indicated by the name of the host which harbours them. 

 We shall have Doliocystis nereidis for the Gregarine of Nereis, Dolio- 

 cystis jwlydorce for that of Polydora, &c. 



Thus the confusion resulting from the union under the same 

 name of genera essentially distinct will cease, and the group 

 Dicystidea will therefore comprise two important genera : — 



(1) The genus Schneideria, peculiar to the digestive tract of 

 terrestrial Arthropods ; 



(2) The genus Doliocystis, peculiar to the digestive tract of 

 marine worms. — Comptes Renclus, t. cxvi. no. 5 (January 30, 1893), 

 pp. 204-206. 



