CELL DIVISION IN EGGS OF CREPIDULA. 519 



abandoned this view and now (1909) thinks that both poles of the spindle are 

 alike and are positively charged, while the chromosomes are negatively charged. 



Schticking (1903) and Delage (1908) found that artificial parthenogenesis 

 may be induced by an electric current, but they made no study of the effects of 

 the current on cell structures. R. Lillie (1903) showed that isolated nuclei and 

 spermatozoa, suspended in cane sugar solution, through which an electrical cur- 

 rent is passed migrate with the negative stream, while cells with voluminous 

 cytoplasm migrate with the positive stream. He concluded therefore that the 

 colloidal particles composing the chromatin carry negative charges, the cytoplasmic 

 particles positive charges. 



In four subsequent papers on the physiology of cell division R. Lillie (1905, 

 1910, 191 1 1 , 191 1 2 ) points out many parallels between electric and mitotic 

 phenomena. In the first of these papers (1905) he holds that "the disposition 

 and relative positions of many colloid aggregates in the cell, especially the 

 chromosomes and chromatic filaments during mitosis, indicate that mutual 

 electrostatic attractions and repulsions play an important part in determining 

 their position and movements." The formation of the spireme and of the 

 equatorial plate, as well as the arrangement of the chromosomes with respect 

 to one another and to the poles of the spindle in amphiasters and triasters was 

 simulated by the use of floating magnetized needles exposed to the attractive or 

 repellant action of magnetic poles. Such models were held to indicate that the 

 astral centers have a repellant action on the chromosomes and therefore, since 

 chromosomes are negatively charged aggregates, these astral areas must also be 

 negatively charged. In the last of the papers cited Lillie (1911 2 ) concludes 

 "that by taking account of the changes of potential resulting from alterations 

 in the permeability of electrically polarized membranes certain characteristic 

 phenomena of mitosis are susceptible of consistent physico-chemical explanation." 



Pentimalli (1909, 1912) and McClendon (1910) confirm Lillie's conclusion 

 that the chromatin bears a negative charge, but McClendon is unable to confirm 

 Pentimalli's observation that in the root-tip of the hyacynth the chromosomes 

 are carried through the cell walls toward the anode. He finds however that the 

 basophile substances of the cell, as well as the mitotic figures as a whole, migrate 

 toward the anode. Roux (1891) found that a "morphological polarization" 

 of the egg substances of different animals, not unlike the stratification produced 

 by centrifugal force, was caused when an electric current was passed through the 

 egg. All of these effects are undoubtedly due to convection currents within cells. 

 Baltzer (1908, 1911) has criticized the views of Hartog and Gallardo, showing 

 that triasters and tetrasters in echinid eggs demonstrate that the poles cannot 

 have opposite signs and that spindles may form where there is no chromatin. 

 In his later work Gallardo (1909) admits that all poles are alike in sign, but denies 

 that a true spindle may be formed where there is no chromatin. He affirms that 

 spindles without chromatin are only apparent, and never lead to cell division. 

 One may admit the truth of the latter half of this statement without granting 

 that the first half is true. Certainly cells do not usuaUy divide if chromatin is 



