SPERMATOGENESIS OF TENEBRIO MOLITOR. 373 



matin. This, I believe, has not been hitherto described for any 

 form and is the phenomenon so effectively brought out by the 

 safranin-licht-griin process of staining, the linin staining a clear 

 green, the chromatin a deep rich red. By no other staining 

 method that I used was this differentiation clearly brought out. 

 In almost all preparations these loops appear to be homogeneous, 

 as Miss Stevens has drawn them in her paper ('o5a). Figs. 5, 6, 

 7, and 8 show several stages in this process of loop-formation. 

 How this transformation is brought about I did not determine. 

 At this stage there is usually some amount of green-staining 

 material mixed in with the chromatin mass. Whether the linin 

 of the loops comes from the chromatin or from this diffuse green- 

 staining material I did not determine. 



There are always ten or fewer chromosomes in sections of cells 

 at this stage, which is the period of general growth. The chro- 

 matin at the tops of the loops thickens and becomes dumbbell- 

 shaped, and both the cell and the nucleus nearly double in size 

 (compare Figs. 8 and 13). 



Toward the end of this period of general growth, the loops 

 begin to straighten out and then to become attached to each 

 other by their linin ends, thus forming the spireme (Figs. 9, 10 

 and 12). The spireme never becomes diffuse, but retains this 

 appearance of dense chromatin masses, like dumbbells, strung 

 upon a linin thread. This thread gradually becomes fainter 

 and more slender, until at the stage just preceding the first 

 spermatocyte division, it is seen as an almost indistinguishable 

 double line connecting the chromosomes (Fig. 13). Rarely 

 during these later stages can a chromosome be found in a tetrad 

 form (Fig. 12). 



Fig. 14 shows these ten bivalent chromosomes in the prophase 

 of a first maturation division, which is the reductional division. 



CONCLUSIONS. 



1 . No stages were found intervening between the last spermato- 

 gonial telophase and the contraction stage. 



2. When the chromosomes have fully emerged from the con- 

 traction stage, they are in the form of loops, and are in the reduced 

 number. 



