628 GRIFFIN. 



All of the figures from camera outlines. 

 EXPLANATION OF PLATE XXXI. 



{Thalassema mellita.') 



Fig. I. Cluster of minute ova in spireme stage; occasional indications seen of 

 the longitudinal splitting of the chromatin-thread. 



Fig. 2. Cluster further advanced ; spireme transversely segmented into flat- 

 tened ellipses ; growth period already entered upon. 



Fig. 3. Cluster much further advanced ; persistence of chromosomes as flat- 

 tened ellipses within germinal vesicle. 



Fig. 4. Cluster of nearly full-grown eggs ; persistence of chromosomes ; forma- 

 tion of alveoli in meshes of cytoplasm. 



Fig. 5. Full-grown unfertilized egg, still in brood-pouch ; persistence of chro- 

 mosomes, rectangular disposition of cytoplasmic strands. 



Fig. 6. Egg one minute after fertilization, showing persistent chromosomes 

 and multiple "asters." 



Fig. 7. Three minutes after fertilization, showing definitive asters. 



Fig. 8. Later stage, asters pushing in wall of germinal vesicle. 



Fig. 9. Same stage, showing variation in relation of asters to germinal vesicle. 



Fig. 10. Spindle nearly completed, chromosomes in two groups. 



Fig. II. Spindle completed, still central; chromosomes, discarded nuclear 

 reticulum, nucleolus. 



Fig. 12. First polar spindle, radially situated, early stage of chromosomes. 

 Sperm-head at ^ . 



Fig. 13. First polar spindle, showing variations in form of chromosomes. 



Fig. 14. First polar spindle, showing later stage of chromosomes. Achro- 

 matic structures in this and preceding figure entirely schematic. 



Fig. 1 5. Anaphase of first polar division ; chromosomes diverging as daughter- 

 V 's or double rods. 



Figs. 16 and 17. First polar telophase, showing double chromosomes. 



Fig. 18. Second polar amphiaster undergoing rotation. 



