MATM:ATI. A Of MM: \ QO, AM. n , , i.- - 01 i i i i i : i - . : LA. 31 

 of th.- nucleus which one encounters in the animal ai.d regettbll 



kingdoms ill staiM-s preparatoiy t.. o-ll division. 



The nucl.ar spindle, the more pn-rise Mnict-ire of \\hich will I,,- 



ribed later, in .liM-uin- the process of cleavage, pur>urs still 



further the direction alrca.lv taken l,y the irermin u-le, until 



it touches with its apex bhe surf ace <>f the yolk, when- it i 

 pcsition with its long axis in the direction of a radius (fig. 1:; / 



miino process of cell-division ><;on takes place hen-, \\hich i 

 h. distini:ui>he.l fivni the oi-.linary n-11 division onlv l.v thi>, 

 the t\\i products of tho division are of very unequal >i/.e. To be 



Fig. 12. Portions of eggs of Asterias glacialis. They show the degeneration of the germinatire 



Teaicle. 

 In figure A it begins to shrivt-1, in th.it a protuberance of protoplasm (x), with a rail 



i>f it, lu-iu-t rates into its interior, and dissolves tin- mrinl>t.ine at that point. UK- 

 _ iiniii iti\>> dot (kf) is still visible, but x-p.u.ttfd into two substances, nuclein (nu) and 

 ]aranurl,'in 



in /' tin- -rriuiii:iti\<- \.-siole (kb) is entirely shrivelled, its membrane is dusolved. and 

 . nly .-null n-i-iii.-nt- ..f tin; KcnniiKitive dot (Ly") reui.iin. In the re-ion of the prot 

 protuberance of figure A there is a nuclear spindle (.*p) in process of formation. 



more exact, therefore, we have to do here with a r< '/' -////././/////. At 

 the place where the nuclear spindle touches the surface \\ith one of 

 \treinities tho yolk arches up into a small knoh. into which 

 half <f the >pir.dle itself advances (ti^. l;j // ). The knob thereupon 

 becomes constricted at its l>ase. and with the half of the spin.! 

 from which sule<jiient ly a vesicular nucleus i- again formed i- 

 detached tVom the yolk as a very small cell (tUr. !'> /// "' ' Here- 

 upon exactly the sallie pr< Ce>s i> I'epeated, after [} : the 

 spiiidl.- which remain- in the t .^r, without havini: pn-\ : 'ored 

 into tho vesicular |uiescent stage of the ntu-h-us. 

 to a complete spindle (t\g. 13 IV). 



There now lie c-lose t, ;rface of the yd 



sphei-ules, which consi.^ of jn-otoplasm and nucleus, and theiefore 

 have the value of small cells (fig. 13 V rk\ rk : ), and which are 

 often to be idtntitied in an unaltt-ied condition. e\en ; 



baa boon divided into a number of cells. They were already 



