PLATE 3 



EXPLANATION OF FIGURES 



Hydractinia echinata 



23 Nucleus just before the reappearance of the chromosomes, showing the 

 homogeneous ground-substance devoid of chromatin net and the nucleolus already 

 much reduced in size. X 600. 



24 Chromosomes reappearing in the nuclear area, the nuclear wall having 

 broken down. X 600. 



25 to 28 Four stages of nuclei in the early growth-period, showing the disap- 

 pearance of the nuclear net by the chromatin arranging itself in crosses and 

 parallel threads which become gradually fainter. X 1225. 



29 a The reappearance of a chromosome, just before maturation, in the 

 form of a cross, the nucleolus with many vacuoles, b, nucleolus with one large 

 vacuole. X 1225. 



240 



