124 KANSAS UNIVERSITY SCIENCE BULLETIN. 



except for the muscle, which it equals. Considering the metaphase 

 alone the average is less than any of the other metaphases for 

 No. 628, the same in No. 629 and the same in No. 630. 



Considering the chromosomes of the connective tissues we find 

 the average diameter for No. 628 to be .767 ,", for the metaphase 

 alone it is .73 v with the greatest diameter found in the anaphase. 

 In No. 629 the average is .735 ," and the greatest diameter is found 

 in the metaphase. The extremes of the averages being .55," and 

 1.20 ,". In No. 630 it is .65 ," and for the metaphase it is .73 ,", this 

 being again above the anaphase. Here again we find the greatest 

 diameter in the younger, and decreasing with age, but for the 

 metaphase alone it is greatest for No. 629. 



Comparing those of the connective tissue with those of the 

 other tissue we find the total average less than for any of the others 

 in Nos. 629 and 630 but greater than those of the muscle or pig- 

 ment in No. 628. 



It is quite conclusive from these figures that there is a difference 

 in chromosome diameters due to age, and that there is a difference 

 in different tissues of the same age, but this variation is not 

 constant. The diameter is neither constant in all phases of the 

 same tissue, as Meek declares, nor is it the same for any one phase 

 in all the tissues. The diameter is not necessarily constant for 

 all the chromosomes in any one somatic cell of any particular 

 tissue, although it is possible this may occasionally happen. The 

 diameters of the chromosome of the neuroplasm and the ectoplasm 

 decrease as the age increases. 



It was practically impossible to find cells where all the chromo- 

 somes of a complex lay in a plane perpendicular to the line of 

 vision so that one could make accurate measurements of the 

 lengths and diameters of all the chromosomes of a complex, as 

 will be seen by noticing in Figs. 2, 3, 4, and 5 the various positions 

 of the individual chromosomes. The dimensions of 25 chromo- 

 somes were taken and the volumes worked out to see if any 

 constancy existed there. The ends were considered to be rounded. 

 The two ends making a sphere whose diameter equalled the 

 diameter of the chromosome and the intermediate space being a 

 cylinder, whose diameter is the diameter of the rod and the length 

 equal to the length of the chromosomes, less its diameter. The 

 volumes ranged from 1.54 cu. ," to 17.94 cu. ,". In a single cell 

 the lengths ranged from 7.5 ,"• to 10 ,", and the diameter from .63 y- to 

 1.00," and the volume from 2.84," to 5.63 cu. ,". 



*Meek ('12) declares that the diameters of the chromosomes 



* C. F. U. Meek. A Metrical Analysis of Chromosome Complexes. 



