.60 SOME ASPECTS OE CELL-CHEMISTRY AND CELL.PHYSLOI.OC Y 



tion-sphere. The fate of such eggs was not determined, but they 



orm a complete demonstration that it is the centrosome and not the 



nucTeus that is the active centre of cell-division nr the cell-body. 



S arce y less conclusive is the case of dispermic eggs m sea-urchms_ 



In" ch e-s both sperm-nuclei conjugate with the egg-nucleus and 



In sucn e,,„s uou i cleavage-nucleus, 



both sperm-centrosomes divide (I^ig. ui^-, '"%,', =„somes 



therefore arises by the union of thtrc nuclei and fow centrosomes. 



S tl :;;;' nvaria&y divide at the first cleavage into four eqtjal b a - 



tomerereach of which receives one of the centrosomes. The lattci 



must, therefore, be the centres of division. 



The statement that the centrosome is an organ f° ^f ■^'™^™ 

 does not, however, express the whole '"''^ I '"■- /" '"^^^f^'t 

 pigment-cells the astral system formed about it is de™ted, a there is 

 go^d reason to believe, not to cell-division, but to movements of the 



p.- ,„ ^ Egqs of Ascuri, will, siipernumeraty centrosome. [BOVERI.] 

 A. Fi,,,!l»i«pi„d; above, isolMed ce„.,os„™e below. B. Res„,. o, ,l,e ensuing d.v.s.on. 



cell-body as a whole ; and, moreover, amitotic division may appar^ 

 ent V take place independently of the centrosome. The ,ok ot the 

 centi-oTome and attraction-sphere in gland-cells (where they are some- 

 Zes very large) and in the nerve-cells is still wholly problema.icah 

 would seenC therefore, that the primary function o the centi^on e 

 L to organize an astral system, of which it forms the focus, that 



Thw an apparatus for mitotic division, but may secondardy 

 ^ec^^'de'teTto o^er functions. The nature of the energy by 

 whTchthi organisation takes place is almost wholly m the dark^ 

 The extraordinary resemblance of the amphiaster to the lines , 

 Ir e i?a magnetic field has impressed many "^---ied^d! -^ 

 hns iiroved that the axis of the mitotic figure is not affected, cuuin„ 

 itrformattn, bv a powerful electro-magnet. The molecules or micro- 



, rlus pl,en„,ne„„„ w.s fust observe,, bv He,..i,.. and »''«-'* ^>„°^''^'''- ' '"" 

 repeateclh observed U,e Internal changes in .be bv.ng eggs of r«../»e„./«. 



