520 CELL DIVISION IN EGGS OF CREPIDULA. 



lacking, though this has been observed by Ziegler, Wilson and others, but the 

 initial spindle (netrum) is formed without the presence of chromatin in the 

 spindle, and perfect spindles of full size may occur without any trace of chromatin, 

 as Boveri (1897) and Baltzer (1908) have shown, and as is figured in figs. 73 and 

 90 of this paper. 



The fundamental difficulty with Gallardo's theory as a theory is its incon- 

 sistency. If the poles of the spindle are of like sign, as he now holds, and the 

 chromatin is of opposite sign, the movements of chromosomes toward the poles 

 in the anaphase find an explanation, but not their movements into the equatorial 

 plate. To explain the latter, Lillie supposes that astral centers and chromatin 

 are of the same sign, viz., that both bear negative charges, but this would not 

 explain the movements of the chromosomes toward the asters in the anaphase, 

 for two daughter chromosomes not only separate from each other, but they cling 

 to other chromosomes and as plates move close to the poles; such movements 

 cannot be explained by assuming that centrosomes and chromosomes bear like 

 charges and hence repel one another. Leduc (1902, 1904) holds that the mitotic 

 phenomena cannot be explained as the result of electric phenomena, whereas they 

 may be the result of diffusion phenomena. About the same time (1902) I main- 

 tained that astral radiations are diffusion streams, and the results of later work 

 have not caused me to change this opinion. Mitotic phenomena are complex 

 and they are doubtless due to several factors, rather than to a single one. 

 Damianovich (1907) believes that several forces may be at work, viz. electricity, 

 polarity, diffusion phenomena, surface tension, hydrostatic polarity and probably 

 different chemical energies ; and Gallardo (1909), to whose review I am indebted 

 for a knowledge of this paper, apparently approves this conclusion. Stomps 

 (1910) holds that the separation of chromosomes is due to the formation and 

 growth of vacuoles between the daughter chromosomes. But it is evident 

 that the phenomena of mitosis and their causes must be more specifically 

 analyzed before we can construct theories as to the mechanics of the process. 



If the mitotic figure is the expression of electrostatic charges carried by 

 colloidal particles composing the chromosomes, centrosomes and cytoplasm it 

 seems probable that the figure would undergo modifications of form or on ® nta " 

 tion if an electric current were passed through it, and such modifications should 

 throw fight upon the nature of the charges carried by different portions of the 

 figure. With this thought in mind I have sub j ected the eggs of Crepidula, during 

 cleavage, to the action of a constant current. In my first experiments with the 

 electric current, which are catalogued at the end of this paper as Nos. 995-W ' , 

 the eggs, stiU within their capsules, were placed in a paraffine trough abo 



5 cm. long, 1 cm. wide and Y 2 cm. deep, containing a small quantity of sea water 



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In Exp. No. 1120 the trough was 12 cm. long and about 2 cm. wide and 1 cm. de p 

 In the paraffine wall at each end of the trough a boot-shaped porcelain *ecu_ 

 was imbedded, with the toe projecting into the trough. Dilute copper suip 



