M'CLUNG : SPERMATOCYTE DIVISIONS OP THE LOCUSTID.K. 197 



or if one or two from the fragment of another cell are in the 

 neighborhood. All these embarrassments are increased when 

 an independent structure like the accessory chromosome is 

 present. These difficulties exist when the conditions are most 

 favorable, i. c, when the chromosomes are arranged in the 

 equatorial plate ; they become practically insurmountable dur- 

 ing any other stage of mitosis by the intertwining of the chro- 

 matic segments or by fusion of chromosomes in later stages. 



Because of these considerations, I do not put implicit confi- 

 dence in conclusions drawn from numerical relations when they 

 involve the question of whether or not there is a difference of 

 one chromosome between two cells. What I have to say, there- 

 fore, concerning the numbers of chromosomes in the different 

 cell generations of the Locustid testis, I must state as my best 

 judgment in the matter, based upon the most careful observa- 

 tions I could make upon cells showing the elements with the 

 greatest clearness. While I regard them as in all probability 

 correct, I do not rely so thoroughly upon them as I do upon 

 observations of structural details, and have therefore based no 

 conclusions upon numerical relations alone. 



As is stated elsewhere, the number of chromosomes in the 

 spermatogonia appears to be thirty-three. This was ascer- 

 tained by selecting the clearest possible cases of the metaphase 

 that could be found and drawing them under the camera lucida. 

 Subsequent countings were made, and in most of the cells 

 thirty-three chromosomes were found. An inspection of figure 1 

 will show that there is a characteristic arrangement of the chro- 

 matin bodies, the larger ones being on the outside of the group, 

 the smaller within. Amongst the large ones, it was impossible to 

 distinguish the accessory chromosome, but a lateral view of the 

 anaphase shows it clearly. From the fact that it was a single 

 element in the spermatogonia, it was to be expected that an 

 uneven number of chromosomes would appear in this cell gen- 

 eration. 



In the spermatocytes, as in the spermatogonia, the polar view 

 of the metaphase was the stage selected for use in counting the 

 chromatin elements. A large number of cases showed that six- 

 teen and seventeen were the prevailing numbers. The smaller 

 of these is easily accounted for when it is recalled that the ac- 

 cessory chromosome is at one pole of the spindle, and would 



