152 FERNANDUS PAYNE. 



EXPLANATION OF PLATE I. 



Prionidns cnstatns Linn. These drawings illustrate the history of the 

 differential chromosomes and the plasmosome during the growth period. A, 

 about the contraction-phase of synapsis the plasmosome and a deeply stain- 

 ing chromatic body is present ; B, the spireme stage following synapsis ; C, 

 the chromatic body is breaking up and a plasmosome is forming around it ; 



D, the stage following C the two plasmosomes have commenced to fuse ; 



E, the chromatic element breaks up for the first time into its constituent 

 elements, the differential chromosomes ; F shows the complete fusion of the 

 two plasmosomes ; G gives the typical appearance of the plasmosome and 

 differential chromosomes during the greater part of the growth period the 

 larger differential chromosome has contracted : H, a prophase of the first 

 division the plasmosome has grown smaller and the differential chromosomes 

 are coming out : /, prophase of the first division, where all the differential 

 chromosomes have left the plasmosome. A, B, C, D and are enlarged 

 4,018 diameters; F, G, H and 7, 2,594 diameters. 



