72 SUMMARY OF CURKENT RESEARCHES RELATING TO 



have usually been placed in the Ceratiese. Mangin finds that when the 

 plates of the Peridiniete are difficult to distinguish, they can be rendered 

 conspicuous by boiling in a 5 p.c. solution of potash. 



Cell-division of Peridinese.* — L. Mangin writes of the cell-division 

 of certain PeridinieaB. By making hourly catclies of Ceratium cornutum 

 in a lake at Compiegne, in September 1907, he found that the time when 

 division was most active was 8 to 10 a.m., when the temperature was 

 12°-15° C. ; and that not more than 2 p.c. of the individuals captured 

 showed signs of division. Two individuals result, and each bears one 

 half of the original cuirass, or cell-wall, and the new half cuirass is com- 

 pleted in a few hours. As to the number of times which a given 

 individual can undergo division, ]\Iangin is unable to state, but he finds 

 indications of the possibility of several divisions, the half cuirasses being 

 different in strength and development. And he points out that if n 

 divisions take place, the number of resulting individuals will be 2", all 

 descended from the one original ; and that two individuals will always 

 retain (one each) the two halves of the original cuirass which have 

 sheltered 7i generations ; 2 will have a half cuirass of n — 1 generations ; 

 2- a half cuirass of n - 2 generations ; 2" ~ - a cuirass of two generations ; 

 and 2" - ' a cuirass of one sreneration. 



&^ 



Plankton of the English Channel.! — C Cepede giv^es an account 

 of the plankton-flora of the Pas de Calais, in 1906. The plankton of 

 the French coasts of the English Channel has been almost entirely 

 neglected in the past, as indeed has the whole coast of France, except 

 the Etang de Thau, on the Mediterranean (Pavillard, 1903), and the 

 basin of Arcachon, on the Atlantic. Cepede gives the contents of nine, 

 several catches of plankton taken at intervals between February 7 and 

 July 21. He also tabulates all the fifty-nine species in a single list in 

 such a way as to show at once the date of occurrence and the abundance 

 at time of capture. Thus he obtains the seasonal distribution of the 

 species. 



Peridiniales of East Greenland Sea.| — 0. Paulsen describes the 

 marine plankton from the East Greenland Sea (west of (J" W. long., and 

 north of 78° 30' N. lat.), collected during the ' Danmark ' Expedition, 

 1906-8. He treats here of the Peridiniales, giving a list of twenty-five 

 species with remarks and figures. Among them are the two new 

 species, PerkUnium varlcans and Apodinium clidetoceratis. 



Cultivation of the Lower Volvocace8B.§ — H.C.Jacobsen publishes 

 an account of some culture-experiments of some of the lower Yolvocacese. 

 Certain of these latter {GMorogonium euchhtrum, ChJamydomonas, Spondy- 

 lomorumquatprnarium, Polytoma uvella), maybe obtained for cultivation 

 from accumulations of albuminous matter rotting in daylight. In the 

 dark Pohjtoma uvella, and, in some circumstances, Clilorogonium euchlorum 



' ■ * Extr. du vol. publie en souvenir de Louis Olivier. Paris : L. Martheux 

 (1911) 5 pp. 



t Bull. Instit. Oceanogr., No. 201 (1911) 14 pp. (1 chart) 

 t Meddel. om Gronland, xliii. (1911) pp. 303-18 (figs.)- 

 § Zeitschr. Bot., ii. (191(1) pp. 145-88 (1 pi.). 



