228 KATHARINE FOOT AND E. C. STROBELL. 



determination hypothesis in no uncertain terms, and many of the 

 investigators who have studied the accessory chromosomes in 

 insects are equally incredulous, Montgomery, Schafer, Moore, 

 Robinson, Arnold and others. 



We have reserved a description of the later stage of the ger- 

 minal vesicle chromosomes of Euscliistus for a subsequent publi- 

 cation, which will discuss only the chromosome groups in both 

 male and female cells. In the male cells we have traced the 

 idiochromosomes through both maturation divisions and are able 

 to support, in the main, Wilson's results as to their division in 

 these stages. He says, the idiochromosomes remain univalent 

 in the first division, each dividing independently, and in the 

 second division the two separate the small idiochromosome 

 going to one pole and the large idiochromosome to the opposite 

 pole. He gives no details however as to the method of the first 

 division and as we find an interesting irregularity in this division, 

 we believe it is worthy of consideration. As the idiochromo- 

 somes separate in the second spindle, this is presumably the so- 

 called reduction division for this unequal tetrad, and the first 

 division should be therefore an equation division, and both idio- 

 chromosomes should divide longitudinally, if the significance that 

 has been attributed to the longitudinal and transverse divisions 

 of the chromosomes holds true in this form. 



The value of the significance of a longitudinal or transverse 

 division is based on the assumption that the so-called ids are 

 arranged in a row, and a morphological demonstration of this 

 assumption is claimed for those cases in which the chromosomes 

 are rod- or thread-shaped these rods or threads often appear- 

 ing as a single row of chromomeres. 



In our smear preparations of the testes of Euscliistus variolar- 

 ius both the large and small idiochromosomes are distinctly rod- 

 shaped, and at the late first prophase and metaphase it can be 

 clearly demonstrated that the large rod divides longitudinally and 

 the small rod transversely. There are rare (perhaps only appar- 

 ent) exceptions to this, but as a rule one divides trans versely /?/-$/ 

 as surely and as constantly as the other divides longitudinally, and 

 this we have demonstrated in a number of photographs. 



The germ cells are being studied in order to obtain a morpho- 



