1 , 2 ROBERT T. H.\NCE 



Spermatogon ia 



Total length oj the chromosomes. The total lengths of the chro- 

 mosomes in the spemiatogonia at 20.400 magnification were 

 found to range from 11S.6 centimeters to 177.6 centimeters with 

 an average of 13t).9 centimeters. A glance at figm'es 1 to 20 

 will show the reason for this wide variation. Cells differ consid- 

 erably in the size of the chromosomes, although it is apparent 

 from the figures and from the measurements, that each chro- 

 mosome of a cell suffers equally in any reduction or gains propor- 

 tionally in an increase of size. I have reported the same con- 

 ditions, rather more marked, in the somatic cells of the mosquito 

 Hance '17 a . This may be due to differences in nourishment, 

 or, as in the case of the production of extra contractile vacuoles 

 in paramaecium ("17 c), to a rapidity of di^*ision which does not 

 permit the chromosomes time to grow to the limits of their pos- 

 sibihties. A graphic illustration is given in text figure 2 of the 

 TniniTmim . maximum and average length of the spermatogonial 

 chromosomes. 



That figure 14 is a giant cell is readily demonstrated when 

 the chromosomes are measured. Although the total lengths 

 of the sj)ermatogonial chromosomes has been found to var^,' be- 

 tween 118.6 and 177.6 centimeters. th*e chromosomes of figure 

 14 measure 235 centimeters, or 58 centimeters longer than the 

 longest set of chromosomes. 



Pairs and relation of pairs. WTien the chromosomes of the 

 spermatogonia are arranged according to length, it is found that 

 they form a series which falls \ery gradually from the long end 

 of the series to the short end. This may be seen in plate 9, 

 row 1, and it is more clearly shown by the hea^'A' black band in 

 text figure 3. The pairing is not as strikingly obvious as in the 

 case of Oenothera scintiUans, but. considering the chances of 

 error in drawing a large number of small chromosomes, I be- 

 heve that the pairs stand out fairly weU. In the table below 

 the average lengths of the spermatogonial chromosomes are 

 listed. Frequenth- the mates are found near each other in the 

 complex but not always. 



