THE SPERMATOOENESIS OF DOJIESTIC M.\M.MALS. 239 



From the obsorviitiou of tbo spjrm!itj;2;.)uL'il clivomosrjmes ii3 woU sis tlioso 

 of tlie fh"st rtxluftion in the raoiLse, it is conctuvablo that with reganls to tlio sex 

 chromosomes (limorpliism miist exLst amoug the spermatozoa and so a tliffereuco 

 may exist between the chromosomes of male germ cells and of the female. 



The nucleolns : — In the sj^iernuitocyte of the mouse a single large mncloolas 

 apiieai-s \\hilo in tho rubbit two or more can bj seen. Tliosj can not 

 be dLstiugiiishcd from the chromosomes in tha preparation stained with iron- 

 luicmatoxj'liu, while Avith Aüerbacii's method these can clearly Ijo made out. 



The existence of the nucleolus in the spenmitocyte has Ijeen repn-ted 

 by many iuvestigatora in several kinds of animals. In mamuutls it is described 

 by Stevexs ('11), DuESRERG ('03 a), Jordan ('14) and Allen ('18). All tliese 

 investigators, with exception of Jordan ('14), agree tha.t the nucleolus aj^j- 

 pears at the post-synapfcic stage and disappears in the pr.tpluise of the first 

 maturation dinsion. 



Jordan ('14) believed that iu mammals the uucleoU almost invariably 

 disappear liefore the synapsis and can thus produce no confusion with the 

 heterochromosomos in those stages where the hitter are most conspicuous. 



As to the physiological meaning of the nucleoli of the germ cells, 

 Wilson ('19) in accordjince with Hacker's ('99) interpretation stated that, "the 

 nucleoH of the germ cells are, iu some cases at least, accumulation of bj'- 

 producis of the nuclear action, derived from the chromatin either by dii-ect 

 transformation of its substanca, or as chemical cleavage-product or secretions." 



As stated atove in the mouse and also in the r.ibbit the nucleoU apjiear 

 at the xx)st-sjTmptic stage and grow gradually, attaining its greatest size in 

 the prophase. When the chromosomes become stained with methyl-green with 

 •Auerbach 's method, this body logins to diminish in size and finally disappears 

 from view in the late prophase. Moreover it is a remarkable fact that whou 

 the gro^\■tll of the cclLs attains to the maximum, the chromosomes and tho 

 nuclcoh stain simiLirly with Auerbach's method. 



ITaese fiiets force us to the conclusion tLat the nucleolus dtxs not 

 represent an accumulation of the by-products of the nuclear actions but consists of 

 gromid substiUice (pLastiu ?) and nntiitive substance ? wliich is taken up l)y tho 

 nucleus from the cytoplasm ; the latter jirobably used for the growth of the nucleus. 



A similar \dew was propoimded by Montogomery ('12j in his study on 



