ORTHOPTERAN SPERMATOGENESIS 665 



b. Relation of first spermatocyte chromosomes to those of the 

 spermatogonium 



(1) If then we are dealing with a morphologically continuous 

 series we must recognize in the twelve chromosomes of the first 

 spermatocyte the twenty-three chromosomes of the last spermato- 

 gonial division. Regarding one of these, the accessory chromo- 

 some, there can be no question. After the last spermatogonial 

 division it removes itself from the others, often into a separate 

 vesicle, and, during all the complicated changes of the synaptic 

 period, may be recognized as a separate and distinct structure. 

 It does not divide in the first spermatocyte but, in the form char- 

 acterizing it in the spermatogonial metaphase, it passes to one 

 pole of the spindle and is included in but one of the two daughter 

 cells (figs. 36 and 45). In the second spermatocyte, showing the 

 same form as in the two preceding generations, it takes its place 

 in the equatorial plate and is divided like its fellows. In this 

 one case the chromosome may be traced with little change through 

 the whole of this period. 



(2) There remain to be considered the twenty-two other 

 chromosomes. It may be seen in the spermatogonial metaphase 

 that these are not of the same size but form a series, the largest 

 of which is many times the length of the smallest. When these 

 are studied carefully it is found that for each size there are two 

 representatives (figs. 44 and 98). In the first spermatocyte 

 there are eleven chromosomes, each composed of two approxi- 

 mately equal halves, the point of contact being in the middle of 

 the length of the elongated rod. If the chromosomes are mor- 

 phologically continuous there is no other conclusion possible 

 than that we have here the twenty-two spermatogonial chromo- 

 somes united into eleven pairs. Still more conclusive on this 

 point are the conditions in Stenobothrus where not only the 

 duplicate series of chromosome sizes appears, but where, because 

 of variations in fiber attachment, there is found a similar dupli- 

 cation according to form. 



It is probably true that until the relations of the chromosomes 

 during the synaptic phase are definitely determined it will not 



