126 ALICE M. BORING. 



filter paper until the edges of the coverglass were dry, and then 

 the edges were covered with vaseline to prevent evaporation. 

 The value of such preparations has already been pointed out 

 many times by N. M. Stevens. They can be used immediately 

 and will often last a couple of weeks. All chromatic structures 

 are distinctly fixed and stained, and some achromatic structures 

 also. The size of the cells is much larger than in preserved 

 material, due partly, as shown by Dr. Stevens, 1 to actual swelling 

 in the acetic acid, and partly to the avoiding of the shrinkage in 

 alcohol and xylol (Figs. 3 and 4). This method insures the 

 study of whole cells and avoids any danger of missing parts of a 

 cell cut off in other sections. If the material is properly pressed 

 out under the coverglass, there will be only a single layer of cells. 

 All the drawings but one in this paper were made from such 



preparations. 



OBSERVATIONS. 



In each lobe of the testis, the stages of spermatogenesis are 

 arranged in a series from the distal end to the end joining the 

 duct. The spermatogonial number is 17 (Fig. i). Spermato- 

 gonial plates were not frequent but this number was counted 

 clearly in four plates. The size of chromosomes varies somewhat 

 but not sufficiently to study chromosome individuality. Not 

 even the odd chromosome can be identified in the spermatogonia. 



The odd chromosome differentiates itself first in the growth 

 stages of the primary spermatocytes. In the early spermatocytes 

 there is a long piece of the spireme lying close against the nuclear 

 wall, that stains darker than the rest (Fig. 2). This next becomes 

 more condensed and shorter, appearing as several beads. Some 

 of the different forms are shown in Fig. 5. Finally it becomes a 

 solid round intensely staining body in the midst of a nucleus 

 with a very lightly staining spireme (Fig. 3). It sometimes 

 retains, however, a slightly elongated shape in prophase (Fig. 6) 

 and even on the spindle of the first spermatocyte division (Fig. 

 8). A plasmosome is also present during these growth stages. 



In the stages of the first spermatocyte division, the odd chromo- 

 some is easily distinguishable from the others by its single condi- 



1 Stevens, N. M., 1908, "A Study of the Germ Cells in Certain Diptera," Jour. 

 Exp. Zoo/., V., p. 359. 



