37 J- T. PATTERSON. 



PLATE V. 



FIG. 22. One end of a longitudinal section of a polygerm showing three of the 

 twelve primary divisions into which it has been divided by constrictions of the 

 nucleated membrane. X 373. 



FIG. 23. Section of a primary mass showing the process by which it is further 

 divided up into secondary masses by constrictions of the nucleated membrane. 

 X 508. 



FIG. 24. Section of a single isolated, primary mass about at the close of its 

 division into single embryonic masses. X 257. 



