214 CHARLES L. PARMENTER 



A conservative estimate of foreshortening upon chromosome 9 in 

 these cells, based upon computation of foreshortening in my 

 material, amounts to a minimum of 2 mm., which restores in 

 these cells the difTerence in length between chromosomes 8 and 9 

 found in the spermatogonial and the other somatic cells. These 

 same chromosomes in the remaining cell (fig. 13) which lack this 

 difference do not appear foreshortened, but owing to the various 

 sources of error pointed out in the preceding pages, it is entirely 

 possible that such a difference may also be present in this cell. 

 These considerations make it probable that the difference be- 

 tween chromosomes 8 and 9 is present in eleven and possibly in 

 all of the twelve somatic cells which Meves measured. It is 

 beyond expectation that this difference should be exactly the 

 same in every cell whether of the same or of different stages of 

 mitosis. 



2. Meves also observes a difference of 3 to 4 mm. between 

 other chromosomes which theoretically should be homologues. 

 In figure 11 between chromosomes 17 and 18 and between 

 chromosomes 23 and 24; in figure 12, between chromosomes 11 

 and 12; in figure 13, between chromosomes 7 and 8, 15 and 16, 

 17 and 18, 23 an,d 24. 



Attempts to apply corrections for the foreshortening evident 

 in these cells, estimated upon the basis of his drawings as com- 

 pared with similar cells in Ambystoma (figs. 5, 13, and 14), 

 leave the situation about as it was. This is not surprising, con- 

 sidering the difficulty of judging the amount of foreshortening 

 that is conspicuous^ present in some chromosomes and the 

 uncertainty of its presence, or absence, in others. Meves' state- 

 ment quoted above concerning the type of cells used for measure- 

 ments makes it quite possible that a great many of these chro- 

 mosomes are foreshortened in amounts varying from 2 to 5 mm. 

 This opinion is strengthened by his generalized and unprecise 

 statement concerning foreshortening and by comparisons with 

 similar cells in Ambystoma. 



The conspicuous foreshortening in some chromosomes, and 

 the probability of it in others, seriously weakens the validity of 

 his measurements. This is especially true of figures 11, 12, 



