86 bulletin: museum of comparative zoology. 



2, Figure 35 shows the spHt spireme (stage e) from the distal pole. 

 The monosome, forming a flattened plate composed of deeply staining 

 granules imbedded in a lighter matrix, lies close to the pole (on the 

 lower side in the figure) and is connected with it by a flattened process, 

 which occupies most of the polar area. Figures If 2 and 114 (Plate 7) 

 represent variations in the monosome at practically this stage. In Fig- 

 ure 112 the monosome is attached to the pole by two filaments, while 

 in Figure 114 it lies almost directly at the pole. Figure 113 shows a 

 slightly later stage, in which the monosome has become converted into 

 a loop, but still retains its connection with the pole. 



In one individual a very interesting abnormality was found, all the 

 germ cells of the testis showing constantly two monosomes. Unfortu- 

 nately I have been able to find in this individual only one dividing 

 spermatogonium in which the chromosomes could be counted with any 

 accuracy. This cell contained twenty four chromosomes instead of 

 the normal number, twenty-three. In all stages of the spermatocytes 

 two well defined monosomes could be distinguished. Figure 27 

 (Plate 2) shows a primary spermatocyte during stage a in which both 

 monosomes are easily distinguishable. On account of the very thick 

 sections in this series I was unable to determine whether the two 

 monosomes are enclosed within separate vesicles. Figure 37 (Plate 

 3) represents a later stage (d) from the same individual, the two 

 monosomes being clearly shown. Apparently, both monosomes in- 

 dependently pass through the same stages as the single monosome of 

 normal individuals. There is, however, a slight difference, in that 

 one monosome shows a greater tendency to disintegrate than the other. 



C. Hippiscus tuberculatus. 

 1. Autosomes. 



The growth period in Hippiscus closely resembles that already 

 described in Dissosteira. However, on account of the chromatin 

 granules being located at greater intervals along the spireme thread, 

 the formation of the split spireme can be studied here to greater ad- 

 vantage. Figures 38-40 (Plate 3) show a few of the spireme threads 

 at successively later stages. During the early part of stage d (Fig. 38) 

 the sjiireme is composed of a single row of chromatin granules imbedded 

 in a linin thread. x4t a little later stage (Fig. 39) the granules are 

 clearly larger and usually elongated transversely to the linin thread. 

 At the left in Figure 39 is shown a portion of a thread in which the 

 granules show evident signs of division. The spireme at this time is 



