PLATE 7 



EXPLAXATION OF FIGURES 



61 Fusion of two i)ronuclei to form a 'fusion nucleus.' (X 1700) 



62 Fusion of two pronuclei to form a 'fusion spindle.' Nuclear membranes 

 breaking down, both between the two pronuclei, and also in the regions turned 

 toward the centrosomes. (X 1700) 



63 'Fusion nucleus,' showing cleavage centrosomes in position. (X 1700) 



64 Side view of first cleavage spindle. Polar cells also shown. Diploid 

 number of dyad chromosomes present. (X 1700) 



65 Anaphase of the first cleavage spindle, side view. (X 1700) 



66 Polar view of metaphase i^late in a soma cell which has undergone 'diminu- 

 tion,' showing double the diploid number of monad chromosomes. (X 1700) 



67 Side view of metaphase spindle of a soma cell which has undergone 

 'diminution.' (X 1700) 



6S Two-cell stage, showing diploid numbei- of dyad chromosomes in each 

 nucleus. (X 1700) 



598 



