ox THE DEVELOPMENT OF AKANEINA. 85 



Explanation of Figures. 



Fiu'. 1. All iiiiseuiiieiited eyi»-, sliowiriü' the polvofoiîil nreas 

 above yolk graimle.s. (^Liictisa). 2 B (Zei>^s). 



Fig. '2. A segnientatioii egg oï the four-cell stage, showiiio- 

 the rosette-like yolk pyramids, {hijcosa^. 2 B. 



Fig. o. A segmentation <^'g^^, shewing the union of tlie poly- 

 gonal areas with tlie segmentation nuclei. (^Ltjcosa). 2 B. 



F^ig. 4. The same as above, Ijut of a little later stage. This 

 shows that the yolk pyramids become very small and that the poly- 

 gonal areas do not correspond in p(jsition with the yolk granules. 

 (Lijcosa). 2 B. 



Fig. 5. An tgg shewing the primary thickening of the blasto- 

 derm. (^Lycusa). 2 A.. 



Fig. 6. An eiig- ha^'in"; the secondary thickeniusf of the blasto- 

 derm, produced at the margin of the primary thickening. (Liicoaa). 

 2 A. 



Fig. 7. An egg in which the primary thickening has extended 

 enormously, and the secondary thickening is at the margin of the 

 [)rimary one as before. (Lijcosa). 2 A. 



Fig. 8. A section of an egg of the two-cell stage, shewing the 

 division of the yolk, and also y<j'k columns, the segmentation cavity, 

 and the yolk nucleus. (^Jjijcosii). 2 C. 



F^ig. \). A section of an egg (jf the sixteen cell stage. {Lijcosli). 

 2C. 



Fio-, 10. A section of a se^'mentation eg-u' in the stag^e of Fig. 

 3, containing twenty two nuclei. {Liicasa). 2 C. 



Fig. 11, A portion «jf a section of an egg in the stage of Fig. 

 5. (Lijcosa). 2 C. . 



