408 E. R. Downing, 
the cells also are larger. Both then decrease in size during the 
synapsis, the nucleus having frequently a collapsed appearance. 
These changes in volume produce a difference between maximum and 
minimum of about one third the least volume of the cell nucleus. 
These facts came out in making measurements to determine the 
number of cell generations. No uniformity could be obtained in rela- 
tive volumes of spermatogonia, spermatocytes etc., until measure- 
ments were confined to the same phase. The equatorial plate stage 
was selected and herewith are given the tables of average measure- 
ments, made up from the measurement of fifty of each kind of cells: 
Spermato- Spermatocyte Spermatocyte Spermatid stage 
gonia Ist order 2nd order of Fig. 61 
Length of cell 10 u 82 u eee aml yn 
Breadth Se 6:3) & 4.9 3,005 
Length of spindle 82 , OT Does 
Breadth a4 „ 4 „ 3 De 
Probably these measurements are approximately correct, yet 
we cannot be sure of the third dimension of these irregularly shaped 
cells since only two dimensions can be seen in the sections. It was 
consequently found more satisfactory to rely on the measurements 
of those cells which had been largely released from pressure of 
adjacent cells and so had assumed the spherical form. The average 
of these measurements gives the following: 
Diameter of the cells. 
Cube of diam. 
Thataeger (relative volumes) 
Interstitial cells (approximate) JT 1728 
Spermatogonia 1st generation Vou. 885 
2nd 
” ” À 
Spermatocytes 1st order | Ce de 
4 2nd 5A „ 15% 
Spermatids 41 „ 69 
It will be seen that in spite of the growth of the cell mentioned 
as occuring during the prophase, the changes which the cell under- 
goes during division produces a net decrease, at every division. 
