HETEROCHROMOSOMES IN THE GUINEA-PIG. 



rations, the chrom< re <luml>-l>cll sh.iped. as in l-'i-. 20. 



They are, ho\ve\er, rarely so well separatc<l. Fit:. 30 shows 24 

 out of the 2S which should appear in such a plate, and Fi-. ,^i 

 an anaphase in which no attempt wa- n, dr.u all of the 



chromosomes. The-e figures though valueless as a dcmonMra- 

 tion of the number of chronio-omes or of the division and di-- 

 tribniion of terochromosomes, are .J\vn to sho\\- that in 



the guinea-pig tin-: no -uch -. -cond synapsis or nninerieal 

 reduction as ha- la-'-n de-cril>ed l>y C.i: '09, P IO for the 



guinea-chicken, the doi '-hieki-n and for man. also l>y Jordan 



'M -or the opoiim. i '-jileir _ in the sections 



\\liich -ho\\ that tin- number i- nly not n-dn - ed <me half, 



and pio!,,;M\ n,,i n dih .ill. 



iv MA I II 



In the younj 5 as in Othei 'inint-diatelx' 



follouin- in iln- chroin.uin rs in inv-ular i-liimp^ 



:natid stage i- >ho\\ n in 

 pla-.ino-.niH-. an iciated 



\\ilh it in tin !! a lai-^c ma^- of ehrom.itin from 



\\hieh -tr.un! ihirkt: to ihr niiclr.ir mnn- 



liraiif. In a SOmew h f I he enitral elnmp o| 



ehroni.ttiii In-, ,ill . : I, and tin- mn leu- i-oiitain- onl\- a 



f.iinlK staini ienlnm. In the half .^PIWII >prrmato. 



Li-hrd to tin- Sertoli cells, the miel.-n- i- line!\ granular ! 



I'hi^ licnre \\.'- drawn from paralion -t. lined \\ith 



ihioiiin. I'lie iin- \\.i- >taine! a d -ep Mile, and the ime 1 

 ^ramiK - aUo Mut-. at the |>ro\imal end. Tin ire- 



^i\en a> evidence thai ti rm.itid-, and -j >ermato/( ,.i ,in- 



ii"t \i-il>l\ I'imorphie, eaeh of the ti^nre- Ix-jn- t\]>ical for all 

 of the nnelei of ' A In'ell < SCntS. 



->! MM \K\ . 



I . The prolialile miml >er of ehroino-. nr.e-, iii the -perm.it o- ( mia 

 of the -uinea-|ii^ i- 5'-. .uid in the >permato< \ tes J N . 

 2. S\ nap-i-> i- of the para-\ naptic tyt 



; A t\pieal heterochromosome i- pre-ent in the growth stag 



of the lirst >,|)ermaP In metakinexj. thi-, i- separated into 



a larger and a -mailer component, as in many insect-. 



