280 KANSAS UNIVERSITY SCIENCE BULLETIN. 



ZOOLOGICAL LABORATORY. 



vary. Possibly this is due to variations in tlie extraction of 

 the stain during the clearing process. The nucleolus in figures 

 16-19 stains as deeply as does the accessory. In some cysts, 

 where the chromosomes are in the extremely loose or early 

 prophase stage, it may be stained very lightly (figs. 20-22) — 

 a violet instead of a safranin color — while in other cysts, where 

 the chromosomes are in a much more advanced condition, it 

 may still be found staining as homogeneously and as deeply 

 as the accessory, though much more irregular in outline than 

 the latter. However, by the time that the chromosomes begin 

 to condense it has almost entirely lost its color, as in figure 24. 

 Finally, at the stage of figure 26, we find it nothing but a pale- 

 yellow or colorless mass. Along with the loss of staining ca- 

 pacity comes a slight decrease in volume. But although it may 

 appear irregular in outline and colorless, it always retains its 

 homogeneous structure. A count of the chromosomes at the 

 stage of figure 26 was made, which showed eleven ordinary 

 chromosomes, the accessory and one nucleolus. For this rea- 

 son, as well as others, we are quite safe in contending that this 

 permanent structure is not a chromosome but a nucleolus, and 

 we feel still more certain that it is not a second accessory or 

 heterochromosome as Montgomery has described it for S^/r- 

 bula. 



In figure 19 is represented a second densely staining body 

 (t). This seems to be merely the end of a spermatocyte chro- 

 mosome, as indicated by the figure, that is beginning to con- 

 dense ahead of its fellows. It cannot be typical of the cyst, 

 for no other cells were found in the cyst containing an element 

 that could be considered homologous to this. Possibly it is the 

 same structure as seen in K, figures 11, 12 and 13. There are 

 present at times small globules, such as P, figures 16 and 18. 

 They are by no means constant for every cell and therefore 

 have been disregarded. 



Turning to the accessory again, we find it changing from the 

 smooth, compact, lumpy condition of figures 16-19 to a flat, 

 extended condition as in figures 20-22. Sometimes in this 

 state it is extremely ragged (fig. 20) and may be vacuolated 

 (fig. 21), as is often the case in the earlier (lump) condition 

 (fig. 18). In the stage following (figs. 23-28), the accessory 

 as usual manifests its tendency to behave like other chromo- 

 somes, by evolving out of the flat, somewhat fenestrated mass 



