304 E. A. MTNCHIN. 



another obliquely. Hence I do not think the Gregarines of 

 Holothurians can be placed in the genus Diplocystis, though 

 they show a great affinity with it. 



Where, then, are these Gregarines to be placed ? I suppose 

 if a genus is to be made for them, the genus Cystobia, 

 Mingazzini, has the priority; but the genus remains reduced 

 to the mere shell, the name only, for the kernel, Mingazzini's 

 diagnosis, must be changed, and the genus itself must be 

 removed from the family Syncystidse. As a matter of fact 

 I do not consider our knowledge of these Gregarines suffi- 

 ciently advanced as yet to discuss their zoological position 

 within the group Monocystidea. Not until the Gregarines 

 of many Holothurians have been thoroughly worked out and 

 compared can it be known what characters are constant pecu- 

 liarities and what are merely characters of adaptation. It 

 seems to me highly probable that the different species of 

 Holothurians will prove to have closely allied species of 

 Gregarines^ derived from a common ancestor which inhabited 

 the ancestor of the genus Holothuria. In order to obtain 

 characters of classificatory value sufficient to found genera 

 and families, the Gregarines inhabiting allied species of 

 animals should be carefully studied and compared in order to 

 find out in what points they agree and differ. The custom at 

 the present time seems to be, however, to open any animal 

 that comes to hand, and at once describe the Gregarine that 

 inevitably occurs in it as a new genus and species, usually 

 without even giving a figure. Our knowledge of the group is 

 not advanced in the least thereby, but confusion and many 

 vexed questions of nomenclature are stored up for the un- 

 fortunate zoologists of the future. 



I prefer, therefore, to leave these Gregarines for the present 

 in the old genus Monocystis, and to wait for future 

 researches to determine their true affinities. 



As to the development of G. holothurise and irregularis 

 from the sporozoite to the adult form, I have unfortunately no 

 observations to offer. As Biitschli says, " we touch here upon 

 the section which is as yet the darkest in the developmental 



