1905.] Effects of Alkalies, etc., on Eggs of Echinus. 133 



one pole without previous division. (See fig. 22, and lower spindle in 

 fig- 19.) 



Changes in Chromosomes and Reduction in Number. — The short, rod-shaped 

 chromosomes of the organism which we have been examining {Echinus 

 esculentus) do not show typically in its normal maturation or maiotic divisions 

 the appearances described by Farmer and Moore* and others in maiotic 

 division, and by Farmer, Moore, and Walkert in cancer. 



According to Bryee,+ the main changes in Echinus esculentus during 

 maturation consist in a marked shortening and thickening of the chromosomes 

 with reduction in number. Each chromosome divides into two short curved 

 rods with spherical enlarged ends, giving rise to an appearance similar to 

 tetrads. But at no time are there any rings or other irregular figures, as 

 described in so many other organisms, and there is no true tetrad formation. 



B. Hertwig§ has observed in the case of Echinus a formation of bodies 

 described as resembling tetrads, as a result of addition of dilute poisons. 



In our specimens of eggs grown in dilute alkali, we have observed 

 appearances in many cases similar to those shown in the drawings illustrating 

 Bryce's paper. 



As the amount of added alkali is increased, there occurs both a shortening 

 and thickening of the chromatin rods and a reduction in their number. In 

 some cases the appearance of rods is lost entirely, and the chromatin becomes 

 arranged in minute masses resembling tetrads. These changes are illustrated 

 in figs. 24, 25, 26, 27, and 28. Thus in the three strengths of di-sodium 

 phosphate solution a shortening of the chromosomes in fig. 25 is seen as 

 compared with fig. 24, and in the strongest solution, fig. 26, the rods are reduced 

 to dots and the number is decreased to approximately one-half. In fig. 28 

 some of the chromosomes present a tetrad-like appearance. These changes, 

 while frequent in occurrence, are not seen in all the dividing cells in any 

 strength of solution, but occur in increased number in the stronger solution. 

 A peculiar appearance is represented in fig. 27, in which a decided protrusion 

 of one pole of the spindle in two adjacent cells of a blastula was observed 

 beyond the cell margin, as if a polar body were being formed. 



Although it is difficult to count the chromosomes accurately, the reduction 

 in number is obvious on contrasting the weaker and stronger solutions. 



In a fair number of cells, especially in the di-sodium phosphate solutions, a 

 peculiar arrangement of the chromatin is observed, which is illustrated in 



* ' Q. J. M. S.,' vol. 48, 1905, p. 489. 

 t ' Eoy. Soc. Proc.,' vol. 72, 1903, p. 499. 

 % 'Q. J. M. S.,' vol. 46, 1903, p. 177. 



§ ' Sitz. Ber. Ges. Morph. und Phy.,' Mtinchen, 1895. Quoted from Wilson, " The Cell 

 in Development and Inheritance," 1904, p. 256. 



VOL. LXXVII. — B. L 



