190 



ROBERT H. BOWEN. 



'number in most of the cells of one of the large-celled lobes (lobe 

 No. 4 Bowen, '22) of one testis. There are six lobes in the 

 testis of EitscJiistus (Bowen, '22), and in this particular testis I 

 have been able to make counts of spermatogonial metaphase 

 chromosome plates in five of the lobes. In four of these (lobes 

 No. 2, 3, 5 and 6 Bowen, '22) the number of chromosomes is 

 14 (normal for the genus (Montgomery, ! n)), and it is clear 

 from other evidence that the one lobe (No. i ) in which no sperma- 

 togonial divisions could be counted, is likewise normal in chromo- 

 some number. In one lobe (No. 4), however, the chromosomes 

 are very clearly abnormal in number as could be readily told from 

 numerous ir.etaphase plates. The exact number was not easily 

 arrived at because the plates tend to be a trifle irregular, but in 

 one or two particularly good cases I have been able to count 28 

 chromosomes with satisfactory clearness (Fig. /). In adjacent 

 cysts of spermatogonia in which the nuclei are in early prophase 

 stages it can also be easily seen that the chromosomes are present 

 in abnormal number, though exact counts were of course impos- 

 sible. In the growth stages of the spermatocytes and in the 

 spermatic! stages the double number of chromosomes can be sur- 

 mised from the unusually large size of the cells, which increase 

 is shared by the cytoplasm as well as the nucleus. The tetraploid 

 condition is, therefore, present throughout the entire lobe, though 

 not exclusively, for I was able to find an occasional cyst (growth 

 period and spermatid ) in which, judging from the comparative 

 sizes of the cells, the chromosomes were present in the normal 

 number. These facts lead me to suppose that an irregular divi- 

 sion of a germ cell at some very early sta^e gave rise to an 

 abnormal series of spermatogonial cells which formed the bulk 

 of the cells in this particular lobe. Among these, however, were 

 included a few normal cells which evidently gave rise to the nor- 

 mal cysts found scattered infrequently among the abnormal ones. 

 Analysis of the constitution of the metaphase spermatogonial 

 plates with 28 chromosomes should bear out the view that the 

 tetraploid chromosome number represents a simple doubling of 

 the usual diploid group. Unfortunately, the chromosomes in 

 EnscJiistits are not of strikingly different sizes, but in the case of 

 the Y chromosome the difference is sufficiently marked to be read- 



