SPERMATOCYTIC DIVISIONS OF LEPTOCORIS H^MATOLOMA. 317 



are quite large, three pairs are of medium size, while the sixth 

 pair and the accessory chromosome are rather small. On account 

 of their size and shape, one has little difficulty in recognizing the 

 members of the various pairs. 



After a series of successive spermatogonial divisions, the 

 thirteen chromosomes pass through the characteristic synaptic 

 and growth stages, giving rise to six tetrads and one dyad, 

 typical of the primary spermatocyte. These tetrads vary greatly 

 in size, the largest and smallest being easily recognized in Figs. 

 3 and 4. Three of the tetrads approximate each other very 

 closely, and the remaining one is slightly smaller than the 

 largest. The dyad representing the accessory chromosome lies 

 close to the nuclear wall in Figs. 3 and 4, but I have no reason to 

 believe that this is necessarily characteristic. Figs. 3 and 4 

 were selected because in each the entire number is seen, though 

 scattered irregularly throughout the nucleus. At this stage the 

 nuclear membrane is intact and the cell itself has increased 

 enormously in size. 



The tetrads are then drawn into the central plate and there 

 is no question as to their final arrangement Fig. 5 shows the 

 typical position of the various chromosomes in the central plate 

 of the first spermatocyte. I have examined numbers of cells 

 and at this stage have always found the six chromosomes ar- 

 ranged in a ring with the smallest in the center. The accessory 

 chromosome always lies in the circle. Paulmier has found this 

 to be the case in Podisus, Lygceus and Chariesterus, but Henking 

 finds no such peculiar arrangement in Pyrrochoris. 



FIRST SPERMATOCYTIC DIVISION. 



The spindle of the primary spermatocyte is ordinarily rather 

 broad but as the chromosomes begin to pull apart, it becomes 

 in many cases, long and slender. The fibers of the spindle 

 converge at the poles, but no centrosomes could be found in 

 any of these stages. This may have been due to the stains used. 

 The chromosomes in the metaphase plate do not divide syn- 

 chronously. The accessory tends to divide precociously (Figs. 

 8 and 9) and is generally followed by the smallest chromosome 

 (Figs. 6 and 7). As the accessory advances toward the poles, 



