16 SUMMARY OF CURRENT RESEARCHES RELATING TO 



place with the chromosomes as centres. Similar phenomena were ob- 

 served in the eggs of a Nemertean and of a Gephyrean. 



The author cites facts tbat show that the ovum may segment with- 

 out the centrosome and the aster ; and while he resards the chromosome 

 as the most influential part of the cell, he would, as a reviewer says, 

 " depose the centrosome from its assumed role of hereditary monarch." 



" The author sees in these results of adding salts no direct mechani- 

 cal phenomena, but only the reactions of living eggs when stimulated 

 by changed environment. The egg becomes a more living thing than 

 it seemed when we were ignorant of these possibilities." 



Polar Bodies in Urodela.* — The late Prof. J. B. Carnoy and H. 

 Lebrun have published a third memoir on this subject. The following 

 is a brief summary of the more important of their conclusions. Their 

 preceding memoirs led them to the conclusion that the nuclear elements 

 of the polar bodies arise from the broken-down nucleoli. They now 

 find further that the spindle, the asters, and the radiations of the first 

 karyokinetic figure, all arise from the karyoplasm, and are therefore 

 nuclear products. There are neither centrosomes nor attractive spheres. 

 The chromosomes are complex figures formed by the fusion of certain 

 filaments, spherules, and granules, which are produced by the breaking- 

 up of the nucleoli ; they are not identical with the primitive chromo- 

 somes of the oocyte. After taking up their position on the rays of 

 the spindle, the chromosomes undergo two divisions, one equatorial and 

 the other axial. The result is to form ultimately the V-shaped chromo- 

 somes which retreat to the poles of the spindle. The spindle then 

 disappears, and is replaced by a new " spindle of separation," in which 

 there appears the cell-plate separating the polar body. The spindle is 

 later invaded by a number of enchylematous granules whose function is 

 nutritive. 



In general the sexual kineses of newts are similar to those of the 

 Liliaceae, and in neither is there any trace of Weismann's reducing 

 divisions. Owing to some differences of detail the two constitute two 

 different types, but in both the reduction is purely quantitative and is 

 due to the tetrads. These are so important in sexual kinesis and so 

 characteristic, that the latter may be justly styled quaternary kinesis. 

 The primitive nuclear element of the oocyte does not persist uutil the 

 sexual kineses, except in the form of certain granules which re-form the 

 nucleoli, and ultimately constitute the chromosomes. The nuclear 

 substance cannot be regarded as the sole bearer of hereditary qualities. 

 The contradictions between these and the statements of preceding 

 authors are ascribed to the incomplete observations of the latter. 



Phagocytosis during Metamorphosis.f — Alf. Burnens publishes a 

 brief note on this subject. He believes that leucocytes play an im- 

 portant part in tissue destruction during metamorphosis, but doubts 

 their power to attack normal tissues. In Amphibians, at the beginning 

 of metamorphosis, the respirations become slower, and in consequence 

 the respiratory changes are impeded, and certain of the tissues become 

 loaded with carbon dioxide. These tissues begin to degenerate, and the 



* La Cellule, xvi. (1899) pp. 303-401 (4 pis.). 

 f Arch. Sci. Pliys. et Nat., viii. (1899) pp. 182-3. 



