STUDIES ON INSECT SPERMATOGENESIS. 405 



6). Further, in this species, the chromatoid body is shaped like a 

 thick disc, the periphery of which is roughly circular, a peculiar shape 

 which makes possible the determination of the long diameter with- 

 out difficulty, and I have made a series of measurements of that 

 dimension in both large and small cells in spermatocyte, division, and 

 spermatid stages. These show that the diameter of the chromatoid 

 body in the small cells differs from that in the large ones in the ratio 

 (approximately) of 1.0 to 1.2. The thickness of the disc is also in- 

 creased in the large cells. My observations show, therefore, that the 

 chromatoid body varies in size with the cell as a whole, but seem to 

 indicate at the same time that the increase in size is not exactly pro- 

 portional to that of the cytoplasm in this particular species. 



It appears, therefore, that all the cytoplasmic components are in- 

 creased in amount (or size) in the large cells, and that the chromatin 

 content is accordingly the only known constituent in the entire cell 

 which is not affected in polymegaly. This is a point of extraordinary 

 interest, and, taken in connection with the fact that this condition 

 occurs in the germ cells, furnishes an interesting side-light to the great 

 mass of evidence already accumulated that the chromatin plays the 

 leading role in hereditary transmission. Furthermore, the increase 

 in the volume of the formed elements of the cytoplasm in the absence 

 of a corresponding increase in the volume of chromatin in the nucleus 

 suggests a number of interesting possibilities as to the nature of the 

 relation existing between the chromatin and the cytoplasmic con- 

 stituents. Apparently the volume of the cytoplasmic constituents 

 cannot be considered as a simple function of the volume of the chroma- 

 tin in a given cell. 



(b) The effects of polymegaly on mature sperms. — As stated above, 

 Montgomery found in the mature (?) sperms of Euschisius three 

 sizes of heads varying in length according to the size of the sper- 

 matocyte generation from which they originated. His observa- 

 tions were on sections only, so that determination of the total 

 dimensions of the sperm were impossible. I have worked out the 

 "dimegalous sperm" of Murgantia in much more complete form, and 

 some account of their differentiation will be given later; here I wish 

 merely to point out that two sizes of sperms occur corresponding to the 

 two generations of spermatocytes. In sections, the actual origin of 

 the two classes of sperms can be positively traced to the two classes of 

 spermatocytes, and by means of smears, tlie two kinds of sperms can 

 be readily isolated entire. Text-figure 3 gives a general idea of the 

 contrast in structure. The two classes are unexpectedly of about 



