THK CKLL NUCLEUS. 



»53 



ri'liiiMo iiifoi-iiiatioii is iivuiliible us t<> the luiture of tlie Iii|uid 

 couipo.siu<i tliL'sr Viicuoles. Tht* rt-fnictivf powtT is lower tluiu 

 that of the siuTouiidiuj; |ihisinii. wliich circuuistiince alone \r 

 sufficient to ditferentiate theui fiuni the asf(js|M»res with which 

 they are occasiuimlly cuiifoiMiiled hy l)e';inners. since a closer 

 examination will <iiiickly show that the refractive jxjwer of the 

 latter botlies is (in most cases at least) jjreiiter than that of ordi- 

 nary yeast plasnia. This dilTerence l»ecomes particularly apparent 

 when the micrometei- screw i)f the 

 microscope is turned to and fri» a 

 little. Under certain circumstiinces 

 the development (tf vacuoles (which 

 are mostly ^'lohular or oval in shape) 

 may proceetl so far that they almost 

 completely 611 the cells, the residue 

 of the protoplasm lieinj; then reduced 

 to a thin stratum adjacent to the cell 

 walls; or, where two or more vacuoles 

 are present, may foiiu a thin layer 

 between them, ami tiius, to the inex- 

 perienced eye, produce the erroneous 

 impression that a septum has been 

 developed. 



The vacuoles are also tx^casionally 

 ob.served to contain inclusions An 

 instjince (thouirh a comparatively i~ire 

 one) of this kintl, namely, the appearance of crystals or crystalloid 

 sti'uctures, is shown in Fijr. i :; i . Such inclusions have been 

 ob.served by Kaum (II. and HiKuoNVMrs (I.) in the vacuoles of 

 true Sacc/iaroiiii/rcf''s, and by 11. ^^'l^L in those of Myanlfnna 

 and Torula. Jans.sens and Leblanc, on the contrary, are of 

 opinion that these structures are in reality nucleoli. 



A more freipieiitly observed ocmrrence is the presence, in 

 vacuoles, of a bri.skly motile body, of which mention will be uuide 

 at the end of the next p.anijrmph. 



KIO. 151.— CYysUilloid 



ill the vai-iiole <«f a ct-U u( jin-Med 

 vi-asl. Near liy U a dciisf cluster 

 of ;:raiiuU-s. Mogti. 4400. 

 llifruiitimut.) 



• Ajttr 



.^ 251. The Granules. 



In addition to the nucleus, which, .-is a rule, is not visible 

 until the prep.iration has been .st;iine<l. yeast cells «:ener!illy 

 contiiin other orj,Mnised inclusions, which, on the contmry. «lo not 

 require any artificial aid to become visible, but conqH^l the 

 attention of the observer bv their hijiher refnictive power. 

 Since their lustre recalls that of the drops of oil fountl in the 

 cells of hiirhei- plants. »■.;/. in seeds, thev h.ive received the 

 name of •refractive bodies." or formerly, "oil drops' At 

 present they are known asgramiles or niicrosomata. It i> only in 

 very youn>r '"H-^ that thov are not to be tound ; but they 



