260 SUMMARY OF CURRENT RESEARCHES RELATING TO 



but has the leucosine characteristic of Chrysomonads. lu Rhizaster there 

 are speciahzed pseudopodia, but the chromatophores and the cyst are 

 indicative of Chrysomonads. The variations accord ■well with Patrick 

 Geddes's old theory of the cell-cycle, which formulated the tendency of 

 cells and unicellular organisms to pass from phase to phase — encysted, 

 flagellate, amoeboid, and, it may be, plasmodial. J. A. T. 



Orientation in Volvox and Pandorina.— S. 0. Mast (Journ. Exper. 

 Zool, 1910, 27, 367-90, 2 figs.)- Both these colonies orient fairly 

 precisely, and both may be either negative or positive. Dark -adapted 

 colonies are usually positive in weak and negative in strong illumination, 

 never the opposite. Light-adapted colonies are sometimes positive in 

 strong and negative in weak illumination. If dark-adapted colonies are 

 exposed to continuous illumination they are neutral for a short time, 

 then positive passing through a maximum, then neutral again, then 

 negative passing through a maximum, then neutral, and finally positive 

 again. In this state they remain. The reversion observed is dependent 

 on the time of exposure and the intensity of illumination ; it is not 

 primarily dependent on photosynthesis ; the green and blue rays are 

 most potent in producing it. Increase ill temperature causes negative 

 specimens to become positive, and decrease causes the opposite, but 

 neither the degree nor the extent of change in temperature is specific in 

 its effect. The same is true in regard to some chemicals. The state 

 of orientation is dependent upon the physiological state, including age, 

 of the colonies as well as upon the constitution of the culture medium. 

 Reversion in orientation is probably associated with changes in perme- 

 ability, positive orientation being associated with an increase and negative 

 orientation with a decrease in permeability. J. A. T. 



Pseudopodial Network for Food-Catching in a Chrysomonad. — 

 A. Pascher (Arch. Protistenlmnde, 1916, 37, 15-30, 1 pi). Amceboid 

 individuals of a new type of Chrysomonad {Ghrysarachnium g.n.) are 

 united by a network of very fine pseudopodia, lying in one plane. This 

 forms a web which captures food. Minute victims are immobilized when 

 they come in contact with the web. Fresh pseudopodia envelop the 

 prey, which is then digested. J. A. T. 



Crossing of Two Species of Chlamydomonas. — A. Pascher {Ber. 

 Dmtsch. Botan. Ges., 19 J 6, 34, 22.S-46). Gametes of two species were 

 seen to conjugate ; the zygotes showed intermediate characters ; they 

 did not develop as readily as usual. Five heterozygotes were followed 

 to the formation of zoospores, which were four in number, as in the 

 parent species. In four cases two of the four zoospores were like the 

 one species, and two like the other. In other cultures, however, only 

 intermediate forms occurred. In others, one parental form occurred 

 and rather unhealthy intermediates. J. A. T. 



Beatricea not a Gigantic Foraminifer. — Charles Schuchert deals 

 with the nomenclature and standing of this fossil organism, which was 

 originally described as a cephalopod {Aulacera) in 1843. In 1857 

 Billings described the same thing as a marine alga {Beatricea), though 



