258 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Protozoa. 



Life-cycle of Difflugia. — A. Goette (Arch. Protistenkunde, 1916, 

 37, 93-138, 3 pis.). In Diffliigia lohostoma nucleated amoeboid " spores " 

 arise from chromidia. There result asexual macro-amoebaB and conjuga- 

 ting micro-amoebai. The latter grow into individuals which may exhibit 

 either plastogamy or conjugation. In plastogamj, said to be due to 

 hunger, a depressed individual fuses with a better-nourished individual 

 and renews its energy. Conjugation has been attributed to a " chromatin- 

 hunger " which leads one individual to attack another and absorb its 

 contents, notably its chromatin. But in the micro-amoebse the nuclei 

 do not suffer depression, so that their conjugation cannot be due to 

 chromatin-hunger. There must be a qualitative difference between the 

 nuclei of the conjugates, a sort of " sex-hunger." J. A. T. 



Feeding in Sun Animalcule. — Maria Sondheim {Arch. ProUsten- 

 Jcunde, 1916, 36, 52-65, 2 pis.). When a victim touches the pseudo- 

 podia of Actinophrys sol their protoplasm coalesces round about it. 

 This seems to be a signal for division of the nucleus. If another victim 

 is captured a new division occurs, and thus colonies arise. When the 

 booty is of relatively large size, such as Paramecium, which is captured 

 in a big vacuole, there is a multiple division round the vacuole. 

 Reproduction follows as the result of a meal. J. A. T. 



Buccal Amoebae. — J. Mendel (Ann. List. Pasteur, 1916, 30, 286- 

 97). The presence of amoeboid organisms in the mouth of a man is 

 frequent, and is not by any means exclusively connected with alveolar 

 pyorrhoea. J. A. T. 



New Amoeba. — A. Pascher {Arch. ProtistenkuncU, 1916, 26, 

 117-36, 1 pi., 4 figs.). A new marine Amoeba, Dinamceba varians, 

 forms plano-convex cysts in which it divides into 4-8 zoospores like 

 Gymnodinium, but with less marked grooves and apparently without a 

 longitudinal flagellum. Tiie spores become amoeboid in a few minutes. 

 Perhaps we have here to do with a Flagellate secondarily adapted to a 

 holozoic life. J. A. T. 



Pyxidicula operculata. — F. Doflein {Zool. Jahrh., Abt. Anat. 

 Biol., 1916, 39; Annce Biol., 1918, 21, 261-2). This is one of the 

 ThecamoebEB, with a shell impregnated with mineral particles, in shape 

 like a broad hat. In multiplication half of the individual emerges in 

 the form of a regular hemisphere, makes a new shell on its surface, and 

 separates after nuclear division. The food consists of algfB and diatoms, 

 but a diet of bacteria results in a modification race. The shell loses 

 colour and becomes thin, so that the modification-form seems naked. 

 It divides rapidly and the size decreases. The axis of nuclear division 

 becomes longitudinal instead of transverse, and an explanation of this 

 is offered. As to the normal structure, there are no chromidia, the 

 nucleus has a large karyosome and no centriole, there are no true chromo- 

 somes, the nuclear division is a true promitosis. J. A. T. 



