324 BULLETIN OF THE 



there is for the assumption that the physico-chemical changes result in 

 an iiocrease rather than in a decrease of the superficial tension. 



The author locates the causes of the metamorphosis of the nucleus 

 which finally lead to its division in the surrounding protoplasm, as Auer- 

 bach maintains, rather than in the nucleus itself. An evidence of this is 

 to be found in the fact that, if several dividing nuclei occupy the same 

 protoplasmic mass (Infusoria, etc.), they are found to present the same 

 stage of advancement. This is, in his opinion, explainable by assuming 

 that the protoplasm acts alike and simultaneously on all the nuclei. 



Although agreeing with Btitschli as to the location of the force which 

 induces nuclear division, I am not able to rest my belief on the evidence 

 which he brings forward here. I know no reason why one would not 

 be equally justified in explaining the synchronism in the division of the 

 several nuclei by assuming that all the masses of nuclear substance are 

 subject to the same laws and rate of growth, — that each requires the 

 same time in preparation for division. The synchronism of the events 

 is no more an argument in favor of an initiative activity on the part 

 of the protoplasm than on the part of the nuclear substance. There 

 may be no objection to saying that the protoplasm acts alike and 

 simultaneously on all the nuclei; but it might be said, with equal 

 justice, that all the nuclei, being chemically alike, act alike upon the 

 protoplasm, and, being of the same age, act simultaneously. 



In his paper on the development of Heteropods, Fol ('76, pp. 112- 

 114) still maintains opinions already alluded to in connection with his 

 paper on Pteropods. Not only does the nucleus disappear at each 

 segmentation, but it becomes twice fused with the surrounding proto- 

 plasm, and as many times individualized, before the first segmentation 

 (p. 113). The nucleus which has reappeared in the central star disap- 

 pears again to give place to two centres of attraction, etc. " The 

 segmentation takes place in the well-known manner. Then the nuclei 

 reappear in the centres of attraction of the first two spherules, and the 

 same phenomena are reproduced at each of the subsequent segmenta- 

 tions." (p. 114.) The nature of the spindle may be learned from the 

 account given of the maturation spindle. " The stoutest of these (aster) 

 rays are those which pass from one centre to the other in the interior 

 of the nucleus." The fusiform body (Auerbach) he considers to be only 

 the central part of the disappeared nucleus ; it is the body described in 

 Geryonia as the remnant of a nucleus. As to the fibres, they are only 

 striae in the protoplasm (p. 112). 



In his "comparisons et reflexions," the author treats these phe- 



