ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 163 



paper includes a discussion on the structure of protoplasm, and the 

 causation of protoplasmic movement. 



Nuclear Division in Protozoa. * — Prof. P. A. Daugeard criticises 

 the usual statement that the nuclear division of Protozoa is invariably 

 direct. He figures and describes the ordinary process of division, ex- 

 emplified, e.g. in Amoeba polypodia ; the division in Amoeba crystalligera, 

 where the dividing nucleus is drawn out into a thread at the division 

 plane ; the division in Sappinia pedata, where the nucleus divides twice 

 without division of the cytoplasm ; finally, he gives a full account of 

 cell-division in Amoeba hyalina sp. n., in which true karyokinesis occurs. 

 In this form the nucleus contains a large nucleolus, which breaks up 

 before division, and appears to give rise to the chromosomes. Some 

 part of the nucleus also mingles with the nucleoplasm and imparts to it 

 chromatic properties ; this nucleoplasm forms a spindle, in which the very 

 fine chromosomes arrange themselves in an equatorial plate. Later they 

 separate and approach the poles of the spindle. As they do this the 

 spindle becomes pulled out, a process which is continued as the chromo- 

 somes migrate to the poles of the elongating amoeba, until the spindle is 

 represented by elongated fibrils. This the author regards as proof that 

 the chromosomes migrate by their own activity, here as elsewhere ; for in 

 the present case there are no spheres, and as the movement continues 

 after the chromosomes have reached the poles of the spindle, the threads 

 of the latter cannot be the active agents. As the new cells separate, the 

 chromosomes round themselves off and constitute the nucleolus, and the 

 remains of the spindle form nucleoplasm around them. The above is 

 clearly a karyokinetic process, but its simplicity, in the author's opinion, 

 shows that indirect division is merely a modification of the simpler direct 

 division, special emphasis being laid on the conditions exemplified in 

 Amoeba crystalligera. 



V 



Physiology of Pelomyxa. f — Antonin Stole has made a series of 

 observations on the digestion and formation of carbohydrates in Pelo- 

 myxa palustris Greeff. In the first place, a prolonged series of experi- 

 ments has convinced him that the " refracting-bodies " of the plasmodium 

 consist of glycogen inclosed in an envelope of less soluble carbohydrate. 

 Experiments on fasting specimens show that the bodies so far act as 

 reserves that they greatly diminish in size when food is not obtainable ; 

 but they do not appear to be ever completely absorbed, however pro- 

 longed the fasting. Under such conditions they shrink owing to the 

 absorption of their contents, and also become aggregated into groups. 

 It is remarkable that a similar process of aggregation occurs simul- 

 taneously in regard to the nuclei, which likewise collect in groups. 

 Feeding experiments showed that starch, whether raw or cooked, was 

 digested by the Pelomyxa, and led to an increase in size of the refract- 

 ing-bodies. The same result was obtained with cellulose and coniferin, 

 both substances which not improbably form a part of the natural food. 

 On the other hand, proteids (white of egg, fibrin, casein, &c.) and fats 

 (milk, fish-fat) produced no change in the refracting-bodies. The part 

 played by these refracting-bodies is summed up by the author as follows. 



* Le Botaniste (Dangeard) vii. (1900) pp. 49-82 (1 pi. and 4 figs.), 

 t Zeitschr. wiss. Zool., lxviii. (1900) pp. 625-68 (2 pis.). 



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