408 SUMMARY OF CUERENT RESEARCHES RELATING TO 



Study of Nematocysts.* — T. H. Taylor has devised a simple appa- 

 ratus of flexible tubes for illustrating the process of eversion of nemato- 

 cysts. His observations lead him to the following three conclusions. 

 In a semi-discharged nematocyst, when fresh, the true end of the filament 

 is concealed from view, and in consequence its structure cannot be 

 ascertained. When the process of eversion is complete, the fluid-contents 

 are expelled from the end of the filament, which, presumably, at this 

 time opens freely to the exterior. A resting-nematocyst is over-distended 

 and in a state of tension. 



Protozoa. 



Intracellular Digestion in Protozoa. t — S. Metalnikow has studied 

 digestion in Parammcium in particular. The food-vacuoles are due to 

 the action of the peribuccal cilia, and are large around assimilable 

 particles, small around indigestible particles. The number of vacuoles 

 varies with the food, but it is the same in all the members of a culture 

 in homogeneous conditions. The circulation of the vacuole lasts longer 

 in the case of useful particles, for the useless particles are quickly got 

 rid of. 



Alcohol and some other doses stimulate the formation of food-vacuoles. 

 Low temperature retards it. Individuals fed with indigestible stuff, like 

 carmin, cease after a time to ingest any more. There is distinct evidence 

 of selective nutrition. 



Infusorians fed with albuminoid substances show in their vacuoles 

 first an acid and then an alkaline reaction. The latter lasts till the 

 vacuole is expelled. If fed with fats or carbohydrateB, the acid reaction 

 predominates over the alkaline reaction in the food vacuoles. The 

 addition of trypsin to the food quickens digestion ; the addition of 

 pepsin has no effect on the rate. 



Bird Malaria. J — Hans v. Alten has studied Plasmodium [Pro- 

 teosoma) prsecox, which causes bird malaria. He describes the schizogony 

 and stages in the development of macrogametocytes and microgametocytes. 

 The systematic position of the parasite is discussed, and its retention in 

 the 2:enus Plasmodium is confirmed. 



New H8emoproteus.§ — G.'PittalngSidescnheB Haemoproteits cajali sp.n. 

 from the red blood -corpuscles of a Chelonian, Clemmys africana. The 

 kidney-shaped appearance of the schizonts, and the apparent difference in 

 form between schizonts and sporonts (spherical), suggest a reference to 

 Hsemoproteus, but no extra-globular stage was observed, which suggests 

 Plasmodium. 



Study of Stentor.|l — Asa. Arthur Schaeffer finds that Stentor acruleus 

 exercises a selection among the particles that are brought to its food- 

 pouch by the ciliary current. The selection is brought about by changes 

 in the beat of the cilia of the pouch and funnel. Certain particles are 

 rejected by a localized reversal of the cilia ; others are carried to the 



* Proc. Phys. Soc. Edinburgh, xviii. (1912) pp. 235-40 (4 figs.), 



t Arch. Zool. Exper., ix. (1912) pp. 373-499 (2 pis.). 



X Centralbl. Bakt. Parasitenk. Ixiii. (1912) pp. 228-441 (1 pi.). 



§ Centralbl. Bakt. Parasitenk., Ixiii. (1912) pp. 241-3 (1 pi.). 



II Journ. Exper. Zool., viii. (1910) pp. 75-132 (2 figs.). 



