188 MONTGOMERY A STUDY OF THE CHROMOSOMES 



shaped) placed side by side with their long axes parallel. This quadrivalent chromosome 

 shows its nature plainly on lateral view (t, Figs. 182, 183) ; on pole view it may 

 always be told by its greater volume (t, Figs. 185, 18G), sometimes even on pole view it 

 appears slightly constricted (Fig. 186, /), the constriction then denoting the plane of appo- 

 sition of the two bivalent chromosomes of which it is composed; it is placed in the spindle 

 so that the tranverse constriction of each of its component chromosomes lies in the piano 

 of the equator (Figs. 182, 183). 



There are accordingly in the first spermatocyte two bivalent chromatin nucleoli, one 

 univalent chromatin nucleolus, twelve bivalent chromosomes, and one quadrivalent 

 chromosome, in all sixteen chromatin elements. 



In the spindle of the second spermatocyte are found either fifteen chromatin elements 

 (Fig 188) or sixteen (Fig. 187). This disparity in number is produced by the unival- 

 ent chromatin nucleolus not dividing in the first maturation mitosis but passing undivided 

 into one of the two daughter cells (second spermatocytes), for it will be remembered that 

 in the monaster stage of the first mitosis it always lies a little outside of the plane of the 

 equator, nearer one pole of the spindle than the other (Fig. 183, N. 2). The rest of the 

 chromatin elements of the second spermatocyte are univalent halves of those in the first 

 spermatocyte (the first maturation division is a reduction division), namely, halves of the 

 two bivalent chromatin nucleoli, of the twelve bivalent chromosomes, and of the one 

 quadrivalent chromosome. The latter element can be recognized in the second spermato- 

 cytes by its greater size (/, Figs. 187, 188), and it here consists of two univalent chromo- 

 somes placed in apposition ; in the spindle of the first maturation mitosis (Figs. 182, 183) 

 it was so placed that each of its bivalent chromosomes underwent a transverse (reduction) 

 division, just as was the case with the other bivalent chromosomes. 



30. Pcecilocapsus lineatus Fabr. 



Six testes of this species were studied. 



There were no spermatogonic mitoses on my preparations, and I could not determine 

 the relations of the chromatin nucleoli in the rest stage of the spermatogonia. 



In the rest stage of the spermatocytes are found two chromatin nucleoli (N. 2, Fig. 

 189, PI. IV) ; in one testis two additional, very minute chromatin uucleoli seemed 

 to be present, but I could not find them on the other preparations. One of the chromatin 

 nucleoli is very large and clearly bilobed (Fig. 189) so that it would seem to be bivalent ; 

 the other is considerably smaller and apparently always rounded, so that it may be uni- 

 valent. These two chromatin nucleoli are sometimes, but not usually, in mutual contact. 



Pole views of the monaster stage of the first maturation mitosis show always eighteen 

 chromatin elements (Fig. 190). One of these is much smaller and one much larger than 



