214 MARY T. HARM AN. 



are not so readily discerned from the parents, a closer examina- 

 tion shows that the pigment of each parent is distributed in 

 about equal proportions. There is no evidence of dominance nor 

 crossing over, and the proportions of offspring are almost per- 

 fectly Mendelian even in small numbers. 



It is from these grouse locusts that the material for the present 

 paper was obtained. The author wishes again to thank Dr. 

 R. K. Nabours for this material and express her appreciation to 

 him for furnishing her the material at a time when she could 

 use it and for giving her access to his records from which she has 

 been able to know the pedigrees of her animals. 



OBSERVATIONS. 



Only the male germ-cells have been studied. Observations 

 have been made upon the spermatogonial divisions, the growth 

 period, synapsis and the maturation divisions. Special con- 

 sideration has been given to the metaphase plate, polar view, of 

 the spermatogonial divisions, the behavior of the chromatin 

 material during the growth period and the manner of the forma- 

 tion of the first spermatocyte chromosomes. 



i . Spermatogonial Divisions. 



In all three forms the thirteen spermatogonial chromosomes 

 in the metaphase are arranged on the spindle, having the appear- 

 ance of the spokes on the hub of a wheel (Fig. i). As may be 

 seen in a metaphase plate, polar view (Figs. 3 to 12), these 

 chromosomes are in pairs and the members of each pair are 

 approximately of equal size and of similar shape. The accessory 

 chromosome is larger than the two smallest pairs and smaller 

 than the other chromosomes. However, many times the differ- 

 ence in size between the chromosomes of the second and third 

 pairs and the X-chromosome is so slight in the spermatogonia 

 that it is difficult to distinguish them. In Fig. 9, the homologous 

 chromosomes of the different pairs are designated by the same 

 number. 



In the anaphase the chromosomes take a position more in the 

 same direction of the fibers of the spindle rather than at right 

 angles to it as in the metaphase (Fig. 2). The change from the 



