ACCESSORY CHROMOSOMES IN MAN. 225 



ft It iu-titied in ignoring them in the prc-ent di-cn inn. FL 

 repre-em- th* me in the contraction pha-e which is not very 



pronounced in m. in. It will be observred that the two character- 

 i-tic ( hroinatin nudeoli still persist. 



I primar\ -i-nnatocytes when ready for divi-ion. a- has 



alre.i<l\ }>< < ' 1, reveal twelve chromosomes in late prophase 



irly metaphase (Figs. 4, 5). In Fig. 4 the two a< are 



seen at and the remaining chromosomes, jud^in- from 



their in< n-a-ed -i/e and changed form, are bivalent, ivpn. -cnt- 



iin-il imivalent chromosomes of the spermatogonium. 



Thai i ^inal twenty-two chromosomes t \\rnty ha\e 



jiain-d io ii.nn the ten bivalent* of the primary s|x-nnai md 



i\\o h.i\e r< inained unpaired as the accessory chromosomes. In 



\ ii i- no! i \idcntjust which two are the accessories although 



i \\el\e i In - are present. 



li i- ob\ ion- iroin tin- the figures (Figs. 4-9) that there is con- 

 -id< r. (Mr dil!- in the si/e of the various chromosomes ot tin- 



|irim.i! Although the attempt was made ii \\a> 



not found |>o--illr t. . .il\\ i\ -s idrntif\' the individual chroino-'u; 

 Tin : i|n\\ n in -i/r from some three or fcmr large ones to i \\. . 



or ilin . -mall oiu-^ luit the fluctuations in sixe, prohabh dm- lor tin- 

 in. -i pan to diitrtvnces in the effects of fixation to-ctlicr \\ith 

 dill, n in . of extraction of the stain, were too great to render 



idniiilii aiion -nrc. In \vry strongly tlecolori/t-d -ret ion-, 



ill\ \\ln n < oiinterstained with Congo red, one large chromo- 

 some in p.inirular fretjuently exhibited a tetrad-like formati -n. 

 \\hilc ilu- oth.-r l.ii^e ones at times showed in. in or less drliniu- 

 indication- oi l.|.in-. 1 n some cases this was siillicu-ntly niarki-d 

 to interfere with accurate counting. In a very fi-w in>i.u: 

 i \\ I think as io U practically negligible, tlu-n- app-arcrl t In- 

 foiirir-'ii in-tr.ul of the customary twelve chroino-omes, but tin- 

 r\tra < lironio-miu - always took the form of a tiny pair which I am 

 inclined to think had Ixxrome split off from one of the ordinary 

 tetrad- or \\hich had through some chance never entered into tin- 

 proper tetrad formation. They were always united by linin-like 

 -trand- to one or two of the larger chromo-om 



I i--. (.. ~. ^ .md 9 show the two accessories in characteristic 

 p. .-it ion-, ^ide \<\ side. the\ alwa\ s pass entire, considerably in 



ail\ ance of the di\ ided ordinarx chromox .me-. io\\ard one pole. 



