72 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Among other novelties introduced by Stein are the following : — 



The genus Cenchridium Ehrbg., hitherto placed with the Forami- 

 nifera and forming Williamson's Entosolenia, is referred to the 

 Prorocentrin^ from its similarity to Dinopyxis, and particularly D. 

 compressa. Examination of living individuals is desirable before this 

 classification can be accepted. 



Dinopyxis compressa has hitherto been, Stein thinks, erroneously 

 classed as a diatom ( = Pyxidicola compressa Baily, P. prisca Ehrbg. ?). 



The problematical organisms which Ehrenberg obtained from 

 flints and described as species of Xanthidium (distinct from the true 

 species of Xanthidium, which are unicellular algae of fresh water) 

 Stein places in the genus Cladopyxis — the sole genus of the Clado- 

 pyxidse — on account of peculiarities of form which he considers show 

 them to belong to the Plagellata. A species of Cladopyxis from the 

 stomach of a Salpa is evidently very nearly allied to X. ramosum and 

 X. furcatum Ehrbg. 



Cilio-Flagellata-* — G. Pouchet has made some observations on 

 Cilio-flagellates, supplementing those of Bergh.f 



A number of new forms are described, most of which the author 

 hesitates to designate as new species on account of the very rudimentary 

 state of our knowledge, ranging them as varieties in " specific groups." 

 Of Protoperidinium two new species are described, of Peridinium 

 one, Glenodinium three, and Gymnodinium one. No new light (the 

 author says) is thrown on the mode of evolution and reproduction, and 

 the facts observed in regard to the conjugation of Ceratium, the gemi- 

 nation of Dinopliysis, and the segmentation of Ampliidinium " do not 

 seem to agree precisely with one another, and would suggest very 

 great differences in the group which seems, however, to be so homo- 

 geneous and so natural." 



Some species may present themselves in chains which break 

 up to set at liberty the individuals which have arrived at their full 

 development. The origin of these chains remains completely 

 unknown. It seems scarcely probable that they are formed by 

 epigenesis. They seem rather to result from the simultaneous 

 development of a certain number of cells originally conjugated. 



Other Cilio-flagellates (Dinophysis) are found in groups of two 

 individuals, which are destined to separate later on ; others {Amphi- 

 dinium) divide and multiply after the manner of diatoms. 



The mucous cyst, observed by Stein and Bergh, within which 

 fission is said to take place, was never seen, but in some Cilio-flagellates 

 provided with a test (^Peridinium divergens) the body retracted within 

 it was seen to give rise by fission to two new individuals. 



The Cilio-flagellates appear to be directly allied to the Nodilucce, 

 which latter are perhaps directly derived from P. divergens. " Every- 

 thing indicates the closest relationship between these organisms, and if 

 the evolutionary chains pointed out here should come to be directly 

 demonstrated, or if, on the other hand, the peridinian chains should 



* Journ. Anat. et Physiol., xix. (1883) pp. 399-455 (12 figs, and i pis.), 

 t Cf. this Journal, ii. (1882) p. 351. 



