June 12, 1908] 



SCIENCE 



907 



on the contrary, the polarity of the ovum is 

 known to determine, the position assumed 

 by the cleavage nuclei. Therefore, it is 

 believed that in Chcetopterus the ground 

 substance retains its polarity after centrif- 

 uging and that the place of formation of 

 the polar bodies is thereby determined. 



III. As to specific gravity of the cell 

 contents, the so-called gray cap, which is 

 specifically lightest, is made up of residual 

 substance of the germinal vesicle and 

 numerous small granules that are black- 

 ened by osmic acid and are soluble in 

 xylol, hence presumably fat granules. 

 The intermediate or clear band contains 

 the majority of basophile granules; the 

 distal hemisphere contains the acidophil e 

 granules, and of these, those originally 

 contained in the ectoplasm appear to be 

 heaviest. 



The Variability of Zygospores in Spi- 

 rogyra quadrata (Hass.) formed by 

 Scalariform and by Lateral Conjuga- 

 tion, and its bearing on the Theory of 

 Amphimixis: L. B. Walton, Kenyon 

 College. 



With the object in view of obtaining 

 data bearing upon the purpose of amphi- 

 mixis, and the causes tending to produce 

 variability— prohlems which have long re- 

 mained most elusive in everything except 

 theory — a biometrical investigation in re- 

 spect to the comparative variability and 

 correlation in 400 zygospores of Spirogyra 

 quadrata (Hass.) formed by scalariform 

 and by lateral conjugation was under- 

 taken. 



In the first instance (scalariform con- 

 jugation) we deal with the results of con- 

 jugation between remotely related cells be- 

 longing to diiferent filaments. In the 

 second instance (lateral conjugation) we 

 deal with the results of conjugation be- 

 tween sister or adjacent cells of the same 

 filament, a condition closely related to the 



phenomena of parthenogenesis in other 

 organisms. If the conjugation of germ 

 cells from remotely related individuals 

 tends to variability as Weismann and 

 others would have us believe, conversely 

 the union of closely related cells should 

 afford a decreased variability, the mini- 

 mum appearing in parthenogenetic forms. 



The results show a condition directly 

 contrary to this, the zygospores of lateral 

 conjugation being approximately 21 per 

 cent, more variable in length and 31 per 

 cent, more variable in diameter than those 

 produced by scalariform conjugation. 

 Consequently direct evidence is afforded in 

 support of the theory of Hatschek (1887) 

 that sex exists for the purpose of limiting 

 and not for the purpose of increasing 

 variability. 



A comparison of constants, the general 

 discussion, methods of measurements, as 

 well as a review of the literature, particu- 

 larly papers by Warren, Kellogg, Pearson, 

 etc., will be given in the completed paper. 



A Contributian towards an Experimental 

 Analysis of the Earyokinetic Figure: F. 

 R. LiLLiE, University of Chicago. 

 The alternative hypotheses (1) that the 

 poles of the karyokinetic figure (eentro- 

 somes) are centers of force -which acts out- 

 w^ards and exerts its efl'eet at a distance 

 (centrosome theory) and (2) that the cen- 

 trosomes are merely centers of insertion of 

 the organic radii (mitome theory), may be 

 tested experimentally. On the first hy- 

 pothesis, spindles that move through the 

 protoplasm would produce new asters in 

 the form of radiating "chains of force" 

 (Hartog) ; on the second hypothesis the 

 moving spindle would drag the organic 

 radii with it and produce considerable dis- 

 tortion of the karyokinetic figure. On the 

 first hypothesis, not only the rays of the 

 asters, but also the fibers of the spindle, 

 must be interpreted as chains of force, and 



