REVIEWS. 4,19 



Among the Dinifera, the first sub-family, Dinophyi^a 

 approaches most nearly to Adinida, having the transverse 

 groove near the anterior end. The second sub-family, Pen- 

 diniday contains the typical genera, Peridiniiwi, Glenodi- 

 nium, Ceratium, kc, and is distinguished by having the 

 transverse groove about the middle of the body. The third 

 and last sub-family, Gi/mnodinida, contains three genera, 

 distinguished by the entire absence of a membrane. 



It is these naked genera which approach, in a remarkable 

 way, to the ciliata. One species of Gymnodinium, for in- 

 instance, exhibits in the ectoplasm the curious muscle-like 

 myophan-strise so characteristic of Paramcecium, Spiros- 

 totnum, and other ciliate forms. The curious Polykrikos was 

 considered by Uljanin as a Turbellarian larva, and by 

 Blitschli was placed among the Ciliata, in spite of its long 

 flagellum. Bergh considers it as a true cilio flagellate, dis- 

 tinguished by having several instead of one transverse 

 ciliated grooves. It is also remarkable for possessing 

 trichocysts, which, as figured by Bergh, have the closest 

 resemblance to the thread-cells of Coelenterata. 



I cannot but think it a matter for regret that Bergh should 

 be so permeated with " Haeckelismus" as to adopt the 

 custom of calling his classification a phylogeny. The method 

 of showing affinities by genealogical trees or other diagrams 

 is a convenient and commendable one, but to call a natural 

 arrangement of a group, based upon the study of recent 

 forms only, a phylogeny, is a misuse of language, and gives 

 a fallacious appearance of certainty to what is, at the best, 

 only well-founded conjecture. 



One point of great interest in regard to several of the 

 genera is their excessive variability. Bergh's object having 

 been to make a thorough investigation of the group, and not 

 merely to discover new species, he has paid great attention 

 to the varieties of each species, and has succeeded in show- 

 ing, as Carpenter, W. K. Parker, and Rupert Jones, did for 

 the Foraminifera and Haeckel for sponges, that each species 

 consists of a " form-cycle" of individuals, differing so much 

 that the extremes of the series would be ranked, without 

 hesitation, as distinct species, if the intermediate steps were 

 unknown. 



It is from some such form as Gymnodinium that Bergh 

 considers the Ciliata to have been derived, the Peritricha 

 ( Vorticella, &c.) being, according to him, the oldest and 

 least modified subdivision of the group. The interesting 

 genus Mesodinium is in many ways intermediate between 

 the Cilio-flagellata and the Peritricha. It has an equatorial 



VOL. XXII. NEW SEK. E E 



