THE SPERMATOGENESIS OF THE SPIDER. I/I 



violet excepting in the metaphase and anaphase, when they also 

 take the safranin. By some authors this is supposed to be due 

 to the presence of a greater amount of nucleinic acid at the 

 height of the mitotic division and since the two peculiar chromo- 

 somes in the spider show this reaction constantly throughout the 

 maturation processes it seems possible that they are more richly 

 supplied with nucleinic acid than the other chromosomes. This 

 is of special interest when we recall that the nuclei of sperma- 

 tozoa contain a maximum of phosphorus. 



The rod-shaped chromosomes are so numerous that it is dif- 

 ficult to make an accurate estimate of their number but by re- 

 peatedly counting those found in a cross section of the equatorial 

 plate I believe the number to be forty (PI. I., Fig. 2). In such 

 a polar view of the equatorial plate two of the forty chromo- 

 somes are found in a peripheral position, thus reducing the num- 

 ber of other chromosomes to thirty-eight. The ordinary mitotic 

 division occurs in which forty daughter chromosomes are carried 

 to each pole, so it is puzzling to know why Wagner should say 

 " Die Kerne der spermatogonien theilen sich nicht nach dem 

 gewohnlichen schema der Karyokinese aber auch night amito- 

 tisch." During mitosis the two peripheral chromosomes split 

 longitudinally and are equally distributed to the two poles, just 

 like the other chromosomes (PI. I., Figs. 3, 4 and 5). During 

 the telophase when the daughter chromosomes become granular 

 and begin to spread out on the linin reticulum even at the be- 

 ginning of this disintegration - -two are conspicuous because they 

 remain unchanged and in the rest stage these two rods are sharply 

 defined as they lie in the chromatin reticulum. Usually they lie 

 side by side but are sometimes found at a short distance from 

 one another and I am inclined to think that in the latter case 

 they are slightly dislodged by the microtome knife and so become 

 separated (PI. I., Figs. 6, 7 and 8.) 



A word might be said here in regard to the name of the pe- 

 culiar chromosomes. In a recent paper ('04) Montgomery has 

 suggested the general term heterochromosome to include the 

 nuclear elements which have been described under various 

 names, and he then divides them into two groups, according to 

 their origin, as follows: (i) "The accessory chromosome' 



