768 SUMMARY OF CURRENT RESEARCHES RELATING TO 



mcecium excretes substances which are toxic to itself when present in its 

 environment, and these substances are more effective when the organisms 

 are confined in limited volumes of culture fluid. 3. The excretion- 

 products play an appreciable part in determining the period of maximum 

 numbers, the rate of decline, and the like, of Parammcium in hay 

 infusions. 



Fertilization in Ciliata.*--P. A. Dangeard discusses Dehorne's 

 position that there is no real fertilization in Ciliata, and points out 

 sources of error. The author upholds the conclusions of Maupas — the 

 occurrence of fertilization in Ciliata is solidly established. The problem 

 of chromatin-reduction is in process of solution. 



Polymorphism in Flagellates.f — Ch. Gineste has observed that in- 

 dividuals of Trichomastix, and the like, may lose their flagella and 

 move with pseudopodia. Sometimes one flagellum is replaced by a 

 pseudopodium. Sometimes the margin shows sinusoid undulatoiy 

 movement. He suggests that these different forms are related to di- 

 versity of environmental conditions. 



Cuirass of Peridinidas.J — L. Mangin contrasts the resistance that the 

 cuirass offers to digestive fluids, with its rapid dissolution inside micro- 

 scopic animals in the water. He also shows that the cuirass undergoes 

 changes of structure during the individual life, particularly as regards 

 the disposition of the ornaments and the constitution of the sutures. In 

 some species the appearance of the sutures changes very markedly. The 

 variations of the sculpturing in Peridinium oceauicum. P. depressum. 

 P. divergens, P. crassipes, and P. punctulatum, are recorded. In short, 

 the author shows that the cuirass is in several respects very plastic, and 

 that it is necessary to know the limits of change in each species. 



Genus Ceratium.§ — E. Jorgensen gives a monographic account of 

 this polymorphic genus, in which he distinguishes four sub-genera — 

 Poroceratium (Vanhoffen), Biceratium (Vanhoffen) Gran, Amphiceratium 

 (Vanhoffen) Gran, and Euctratium Gran. After describing all the species, 

 the author discusses their affinities, tracing back the other three sub- 

 genera to the Biceratium stock. The variability of species of Ceratiinn 

 is dealt with and the geographical distribution. 



Pleodorina californica at Banyuls.||— Edouard Chatton found this 

 Volvocinid, previously reported from California, Indiana, Illinois, in an 

 irrigation pond at Banyuls-sur-Mer. It appeared at the end of April and 

 disappeared at the beginning of July. It was observed in three succes- 

 sive years, but no sexual reproduction was detected in the pond. This 

 was studied, however, in the laboratory. Vegetative colonies, parthe- 

 nogenetic colonies, male colonies, female colonies, and " involution " 



* Comptes Kendus, clii. (1911) pp. 1703-5. 



t O.R. Soc. Biol., lxx. (1911) pp. 1014-16. 



X Intemat. Rev. Ges. Hydrobiol., iv. (1911) pp. 44-54 (2 pis.). 



§ Internat. Rev. Hydrobiol., iv. (1911) Biol. Supp., pp. 1-124 (10 pis.). 



|| Bull. Sci. France Belg., xliv. (1911) pp. 309-31 (1 pi.). 



