Illl ; .AGE. 65 



spei malic nucleus remain lor a lime separate, e\eii after t hey 



approached each other, After a bri.f period ,,f res? h..th of them 

 be'_'in to exhibit ramultaneously the changi s which precede th. 

 mation of the nuclear spindle. In each the chromatic >un>i:mce is 



metamorphosed into a line thread, which i.s ananged \\ithin tin- 

 nuclear membrane io numerous windings. Kadi filament Kftl 

 upon divided into two equally large coiled loops, the chromosomes 

 (tig. '_'.") fit}. Now the t wo vesicular nuclei lo-e tlnir d.-limitat ion 

 from the Surrounding yolk, in which there ari-i- at a little li> ! 

 from i-ach other two polar corp i> -les [centres i rounded 



in of rays, which is at first taint, hut sultM-tjucntly becomes 

 more distinct. Between the two centrosomes, the method of whose 

 development no one has a- ye 1 -mvee.le 1 in observing, there are 

 formed spindle-fibres, and the four loops (chromosomes), -et free by 



the dissolution of the two nuclear membranes, so arrange t hem- 

 that they He upon the outside of the snindle at its einia 



In the case of the r^r of the Maw worm, then-tore, the union of tin- 

 two >;-\ual nuclei, which terminates the act of tert ilis it ion. take- 

 place only at the time of the metamorphosis to form the dea. 

 spindle, in which metamorphosis they take an eipial >haiv. In conse- 

 quence of this remarkable deviation from the ordinary course of the 

 process of fertilisation. \AN |'.!:\I.DI:\ has been able to establish the 

 interesting and important fact that half of the chron, : t he 



lii->t cleavage spindle are derived from the egg-nucleus, and half from 

 the spermatic nucleus, and that consequent ly they mav be di>tin- 

 guishedas female and mal chromosomes. Since in this in-t ance. ju>t 

 as in nuclear division ordinarily, the four loops are split length ui>e 

 and then moveapirt toward the two polar corpuscle- mes), 



there an* formed two groups of four daughter-loopj each, of which 

 two are of male origin and two of female. Each group i> then n 

 morphoM-d into the qniesc.-nt nucleus of the ilaught-r-ci'll. This 

 furnishes incontestable proof, that l<> inch <ln<jl<t 



<>/ tlt> .//, /////.:// (irises as tltc r<slf ,,/ //,,> jirxt <' 



th> "int of C/ifan, :L (/> 



_ ?/<> *j)>-rntnti<- 



The first division is followed after a brief period f n-t by the 

 second, this by the third, the fourth, etc., during which are repeated 

 the same series of changes in nucleus and protoplasm th it haM- 

 been described. Thus in quick finl daughter-cdls 



are divided into 4, thes- into 8, 1C, 3'?, 64, etc. (tig. 30), until 

 there has resulted a large spheroid il mass, which ha< received the 



