GERM CELLS OF GRYLLOTALPA 313 



my observations confirm his count of the spermatogonial number. 

 The spermatogonial number in the material collected at Naples 

 shows 15 chromosomes. Here we have at least two species and 

 perhaps three in the same genus in which the chromosome 

 number differs. It demonstrates clearly, I think, the fallacy of 

 the argument that all closely related species must have the 

 same number of chromosomes. It further shows the danger of 

 generalizations. 



7. ADDENDUM 



As my paper was ready for the press, I received the final paper 

 of Voinov on Gryllotalpa vulgaris. 3 His observations are very 

 much as in his preliminary papers but more extensive. One 

 difference should be mentioned. He finds 15 chromosomes in 

 some spermatogonial cells, while 14 was the number previously 

 observed. This number (15) agrees with my observations on 

 the Naples material, although the size relations are not the 

 same, as I find two small chromosomes instead of one. Voinov 

 collected his material near Bucharest and it is possible that the 

 chromosomes in the material collected at Bucharest and Naples 

 are different, as they were in the material collected at Naples 

 and Freiburg. Even though our observations may have been 

 made on different forms I cannot agree with his interpretations. 

 He finds seven chromosomes in the first spermatocyte division. 

 One of these seven is a small bivalent which he calls the m- 

 chromosome. He believes this to be the same chromosome as 

 the small one in the spermatogonial group. Hence he is driven 

 to the assumption that the small spermatogonial chromosome is 

 double. There must be at least 16 spermatogonial chromosomes 

 then. Another one of his first spermatocyte chromosomes is an 

 unequal pair, which divides unequally. This he calls the XY 

 pair. As there is only one small spermatogonial chromosome he 

 is driven to make another assumption, that is, that the Y-chro- 

 mosome must be present but not visible. This would make all 

 told 17 spermatogonial chromosomes, two more than he has 



3 Recherches sur la spermatogenese du Gryllotalpa vulgaris Latr. Archiv de 

 Zool. Exp. et Gen., Tome 54. 



