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SUMMARY OF CURRENT RESEARCHES RELATING TO 
It is clear without any staining or fixing. It arises by a sort of 
condensation of the protoplasm within the cyst, by a coalescence of 
alveolar walls and disappearance of spaces and inclusions. Meanwhile 
in the disintegrating karyosome the first generative nucleus appears : it 
passes out of the primary nucleus into the generative protoplasm. The 
latter becomes peripheral within the cyst, forming a hyaline layer, and 
this fragments into as many portions as there are generative nuclei 
(derived from the first by mitosis). Thus the gametes are formed. 
The author points out that there is here a clear case of the protoplasm 
playing an important role in heredity as well as the chromatin of the 
nucleus. J. A. T. 
Intestinal Parasites observed in Malta.— Thomas Bentham 
(. Parasitology , 1920, 12, 72-82). Observations made by the late Lieut. 
T. Bentham on 3370 cases among troops and prisoners in Malta. The 
parasites included Entamoeba histolytica, free Amoebae (not determined), 
other Protozoa, Taenia saginata , T. solium, Hymenolepis nana, Clonorchis 
sinensis, Schistosomum haematobium, 8. japonicum, Fasciola hepatica, 
Trichnris trichiura, Ascaris lumbricoides, Strongyloides stereo r al is, Anky- 
lostoma duodenale. J. A. T. 
Choice of Food in Amoeba. — Asa A. Schaeffer ( Journ . Animal 
Behaviour, 1917, 7 , 220-58). Amoeba is capable of nice discrimination 
between two particles of different composition — one digestible, the other 
not — lying very close together. When the particles stick together 
slightly, the food cup in some way separates them so that the food 
particle comes to lie inside the cup, while the other is actively pushed to 
the outside. The amoeba not only expresses choice between particles of 
different composition, but if the conditions’are such that a choice cannot 
be made at once, the amoeba can change the conditions (separate the 
particles) so that a choice may be made. No definite statement can be 
made regarding the basis upon which choice in general is made, for 
some digestible substances are refused (zein, gelatin) and some indiges- 
tible substances (carmine, indian ink) are readily eaten. It can be stated, 
however, that the basis of selection is not chemical in any known case, 
and that in several important cases selection is based upon physical 
properties. 
Movement of a particle is an important quality. Particles of glass, 
which are never eaten when lying still, are readily eaten when agitated. 
The ingestion-value and the digestion-value are very different. Obser- 
vation and experiment indicate that amoebae might possibly be able to 
exist and propagate indefinitely in nature if they selected their food on 
the basis of movement alone. Experiments show that, in many cases, 
past experience in receiving stimuli or in feeding is of more importance in 
selection than the nature of the stimuli received from a present object. 
Many individual acts of food-selection cannot be explained when standing 
alone, but they are explicable when the amoeba’s past, especially its 
immediate past, is known. Food-selection is therefore an historical pro- 
cess. There is a physical factor in food-selection ; there is also an 
experimental factor. J. A. T. 
