CHROMOSOME GROUP IN BRACHVSTOLA MAGXA. 



and more slender the spiremes, the more pronounced their dif- 

 ferences of volume would appear. Obviously, it is impossible to 

 study the length of convoluted spiremes in sections. Smear- 

 preparations also fail in the spermatogonia on account of the 

 strength of the nuclear membrane, which in these cells resists the 

 roughest treatment and prevents the separation of its contained 

 spiremes. But in the prophases of the primary spermatocytes 

 the nuclear membrane becomes so thin and weak that its contents 

 may be readily smeared upon a cover-glass and the spiremes 

 thus separated and to a certain extent flattened in the plane of 

 the cover. In the most favorable of these cases, such as those 

 shown in Figs. 5, 6 and 7, which represent different stages 

 in the concentration of the spermatocyte spiremes, a more or 

 less accurate comparison by means of measurements is possible. 

 For the sake of convenience in reference, we will designate the 

 chromosomes in these figures by the first eleven letters of the 

 alphabet, beginning with the longest chromosome and proceeding 

 according to size. The chromosomes as drawn are in all cases 

 simple projections and hence suffer a greater or less amount of 

 foreshortening according to the degree of their curvature or in- 

 clination to the plane of the slide. This, however, is so slight 

 that it has been disregarded in the table except in case of 

 chromosomes b and 1i of Fig. 6. In these cases, the actual 

 length in the figure is given in parentheses and an estimate of the 

 real length in the regular column. No attempt was made to 

 measure the three smaller elements, as their variations in form 

 and diameter in the spermatocytes render measurement in one 



NOTE. The figures are in terms of an arbitrary unit equivalent to the distance 

 apart of the divider-points used in making the measurements. 



