mack: dimensions of chromosomes. 123 



1.02 ,". If we compare these figures with the corresponding results 

 recorded for the nerve tissue of Nos. 629 and 630 we notice a 

 marked difference in the diameter, which seems to decrease as the 

 age increases. This holds true with those of the different phases 

 as well. The variation in the averages continues very great. In 

 No. 630 it ranges from .53," to 1.70,". The cells showing mitosis 

 are far more numerous in No. 628 than in the others and the 

 amount of nerve tissue is greater also as might be expected. The 

 results for the other tissues were worked out in a similar manner. 

 The number of cells showing mitosis in the other tissues is much 

 less than in the nerve tissue, so that 21, 15 and 10 were about all 

 the good specimens that could be found in these different tissues. 



In the ectoplasm for No. 628 the general average is .83 ,", for 

 the metaphase alone it is .82 ," with various averages for individual 

 cells ranging from .55 ," to 1.10 ,". If we compare these figures with 

 those for the chromosomes of the ectoplasm of No. 629 and 

 No. 630 we find in one case the average is .775 :> and in the other 

 .75," and for the metaphase alone it is .79," and .75,", with still 

 greater extremes in the general averages ranging from .63 :< to 

 1.20 ," in one case and .57 />. to 1.10 ;>■ in the other. As in the nerve 

 plasm the diameter decreases as age increases. 



In the muscle the average for No. 628 is .663 ," and for the 

 metaphase .67 <>. with a variation in extremes of only .63 ," to 83 ,". 

 Contrary to the action of the chromosomes in the nerve plasm 

 and ectoplasm, the general average of diameters increases in No. 

 629 to .80 ," and .78 ," for metaphase and then decreases slightly in 

 No. 630 to .70," for the general average and .68 ,« for the metaphase, 

 with great variations and extremes. 



The chromosomes of the pigment cells have an average diameter 

 in No. 628 of .725,". The metaphase has a diameter of .715,". 

 The chromosomes in No. 629 of the same tissue has a diameter 

 of .85 ,", the metaphase of .75 ,". The extremes are .65 >>■ and 1.30 ,". 

 The diameters in the pigment cells seems to be greatest in No. 

 629 and least in No. 630 both for the metaphase and for the 

 general average, neither following the results for the nerve nor 

 for the muscle. 



Comparing the results of the pigment with those of the nerve- 

 plasm, ectoplasm and muscle we find that the diameter in No. 

 628 is greater than the diameter for the muscle and less than for 

 the nerveplasm and ectoplasm. In No. 629 it is greater than in 

 any of the others and in No. 630 it is less than any of the others 



2 — Univ. Sci; null.. Vol. TX, No. 10. 



