sQRY CHROMOSOMES IN MAN. 22~ 



VYhile at the < -inclusion of the divisions of the primary sper- 

 mat'K M and twelve chromosomes respectively were delivered 



\'< the pair- of daughter cells, nevertheless, when the latter a- 

 ndary Bpermatocytes become ready for division, half of them 

 -how h\e. mil i In- remainder seven chromosomes. A -.-cond pair- 

 inc "t tin- ordinary chromosomes has evidently occurred, so that 

 tln-n- an- li\<- l.ivalent chromosomes in each type of cell and the 

 additional i v. ssories in the one type. 1 i_ u i- a dra\\ in- 



ns secondary spermatocytes; th< -ho\\> five 



bivalent < hroino-oim-s in late prophase, the other more than ti\v 

 chr"iiio~.,iiir^ in nu-taphase. These two cells art- undoubtedly 

 tin i\\o daii^hii r n Us of the same primary spermat'>i > tr. i 

 i ; "Hi- d.iiii;htiT cell containing a group ol i rhn>ino- 



:iidil)' a late ana phase of division which shows at one 



i-nd five chromosomes. The number of chromosomes at tlu-oppo- 

 site i'li "I the second cell should of course be five although l>r- 

 cause "1 ilu- dm-*- ma--ini; it could not he |M)>iti\d\ drti-rinincd. 



i} represents a late anaphase of division in a aecondar) -pn- 



ma' \\hiih niaiiitt -ily had had seven chromosome*- in nu-ia- 



pli. . 



Both acccssoi nosomes divide in this semiid -pi-niia 1 



!i\i-iini period so that each resulting spennaiid receives 



n chroinMsunu-. (Fig. 16). Fig. 15 reprr-ml> an aiia|)lia-r 



o| ili\ixi,,n in a secondary spermatocyte showing -till at tin- f|iia- 



i"i c.t iln- ~;iindle a laKgmis chnnnatic mass. Smli a rendition 



\\as toiind in --\-ral instances and while I l-lif\- ii to In- tin- two 



hromosomes which happened merely to ! unta\oralil\ 



pla.iillor I.I.M r\ alion, I rould not positi\'rl\ idrniilv it a^ -nch. 



I r. -in tin relative positions of the chromosomes as seen in 11-. i' 



onr \\onld inli-r that the two sets of acce--oric- \\ -n- the la-i to 



have passed from the equator to the poles of the spindle M<>r 

 over, -ni-h a ^ of the accessory in this divi-ion was ob- 



served in 1-oth the guinea and the chicken (Guyer, 'oo . 



It .should l.t- mentioned that occasional di\-isinn stages \\> 

 \isjMc which, judging from the smalhu-ss ol tin- cell and the -\/c 

 and sli,i|e M|" the chromosomes, looked a- it" they miijit he secon- 

 dary spermatocytes preparing to divide with the univalent t\pe 

 iten or t\\rl\i- of chromosome. It i- po ihK-, for instance, that 



