120 bulletin: museum of comparative zoology. 



method of distribution in the maturation divisions, may always move 

 the same way, i. e., all the chromosomes brought into the egg may 

 pass into the female-producing sperm. It is extremely doubtful if 

 the last suggestion will prove applicable as a general rule, but the 

 conditions in Gryllotalpa are interesting exceptions to what has been 

 found in the Acrididae and Tettigidae.^ 



Hartmann ('13) describes small chromosomes as dividing unequally 

 in some male germ-cells of Schistocerca. In one first-spermatocyte 

 cell he found two such chromosomes (tetrads) dividing unequally, 

 and he found some cases of unequal division in the secondary sperma- 

 tocytes. These observations, if correct, would lead one to suspect 

 that he might" have been dealing with a condition similar to that in 

 Phrynotettix, except that in the first division, either both the small 

 chromosomes divided sometimes reductionally and sometimes equa- 

 tionally, or, while one of them followed this method, the other always 

 divided reductionally. 



Bringing together the results of Baumgartner and Payne for Gryllo- 

 talpa, those of Carothers for Acrididae, Robertson for Tettigidae, and 

 my own for Plirynotettix, we may arrange a graded series of condi- 

 tions beginning with (1) tetrad B, in Phrynotettix, which is unequal, 

 but divides equationally in the first division; passing (2) to Ci, which 

 divides with equal frequency either reductionally or equationally in 

 the first division, and when dividing reductionally shows chance 

 distribution with reference to the accessory; thence (3) to the unequal 

 types found by Carothers and Robertson, which always divide re- 

 ductionally in the first division but show chance distribution, and 

 finally (4) to Gryllotalpa, where division is always unequal in the first 

 spermatocytes, but the larger dyad always accompanies the accessory. 

 Whether this series offers any possible explanation as to the origin of 

 these unequal elements, and their different kinds of behavior, is prob- 

 lematical. 



Robertson's work deserves further consideration, because he has 

 found two of the tkree possible combinations which would be expected 

 out of a random recombination of two unequal elements which con- 

 jugate. In the case of Tettigidea, he found the unequal tetrad in 



' i^oslscrij)!. — Unfortunately Jif had [overlooked the results reported for Gryllotalpa vul- 

 garis by Voinov ('14), who found in the first spermatocyte metaphase an unequal pair of dyads, 

 which separate so that sometimes the larger dyad and sometimes the smaller one goes to the 

 same pole as the accessory chromosome. These results are in accord with those mentioned 

 above for the Acrididae and the Tettigidae and it may be surmised that similar conditions 

 perhaps obtain for Gryllotalpa borealis but have so far been overlooked. 



