908 



SCIENCE 



[N. S. Vol. XXVII. No. 702 



the chromosomes as well as centrosomes 

 may be centers of force. Therefore, in 

 any movement of the spindle through the 

 cytoplasm, it is conceivable that its ma- 

 terial also is constantly changing. If, 

 therefore, the karyokinetic figure were 

 suddenly moved from protoplasm of one 

 morphological character into protoplasm 

 of another, comparison of the normal and 

 experimental conditions of the karyokinetic 

 figure would furnish evidence for deciding 

 between the two hypotheses. 



The unfertilized eggs of Chcetopterus 

 •enable us to make such a test. After they 

 have remained in sea water fifteen to 

 twenty minutes, each possesses a large 

 karyokinetic figure fixed at the animal 

 pole, and this figure remains at the 

 mesophase for hours. If such eggs be 

 eentrifuged with relatively low powers 

 (1,150 revolutions in 30 seconds to 1,750 

 revolutions in 45 seconds) not only may 

 the karyokinetic figure be moved through 

 the cytoplasm, or the latter caused to flow 

 past the spindle, but new configurations 

 arise in the cytoplasm, owing to central 

 or peripheral displacement (with reference 

 to the direction of the centrifugal force) of 

 the granules suspended in the ground sub- 

 stance of the cytoplasm. The most im- 

 portant of these configurations for our 

 purpose is a dense accumulation of the 

 basophile granules a little central to the 

 middle point of the egg. This is a new 

 formation called suddenly into existence, 

 within 30 to 45 seconds, and contrasting 

 strongly with the remainder of either 

 normal or eentrifuged eggs. 



If a pole of the spindle enter this 

 basophile mass, the granules of the latter 

 appear to be rearranged in radiating lines 

 that can be interpreted only as chains of 

 force. Apparently the original radiations 

 of the pole in question are lost, or are 

 reenforced. The rays of the aster in the 

 basophile mass are actually more numerous 



than in the karyokinetic figures of control 

 eggs, as determined by counting. 



Any part of the basophile mass that 

 enters the spindle appears also to be re- 

 arranged in chains of force : one finds that 

 the part of the spindle within the basophile 

 mass usually stains correspondingly, and 

 thus contrasts strongly with the part with- 

 out, and this is probably due in the first 

 place to infiltration of basophile granules; 

 but the modified part of the spindle is also 

 fibrous in its structure and the interfilar 

 spaces are empty of granules, so that it 

 would appear that the infiltrated granules 

 are arranged in chains. 



Such distortions as are found in either 

 the rays of the aster or the fibers of the 

 spindle are explicable on the chain of force 

 hypothesis; because it has been shown by 

 Hartog that chains of force consisting of 

 iron dust suspended in glycerine or balsam 

 will bear great distortion before ruptur- 

 ing; and this is due in the first place to 

 the fact that the longer path of a distorted 

 chain is more permeable than the relatively 

 resistant medium in which the permeable 

 chains of particles are embedded, and in 

 the second place (to a certain extent) to 

 the viscosity of the medium. 



The mitome hypothesis appears inade- 

 quate to explain the results of the experi- 

 ments, and may certainly be regarded as 

 disproved if actual counts show a definite 

 increase in the number of astral rays pro- 

 ceeding from the pole embedded in the 

 basophile mass. 



If the center of force hypothesis be ac- 

 cepted, the results show that the basophile 

 granules are extremely permeable to the 

 "mitokinetie force" (Hartog) and that 

 the ground substance is highly imperme- 

 able. Acidophile granules are also im- 

 permeable; or at least they are not 

 arranged in chains of force. 



The Pacific Scientific Institution: Wm. A. 

 Bryan, Honolulu, T. H. 



