3 • THE UNFERTILIZED EGG AND ITS 

 ORGANIZATION FOR 

 DEVELOPMENT 



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T Ten 



e now proceed to face one of the most difficult problems in embry- 

 ology — that is, the organization of the unfertilized egg with respect to its 

 development into the structures of the adult. From a chemical standpoint the 

 egg after ovulation is not strikingly different from any other cell in various 

 parts of the body. The physical consistency of the egg cell is not very different 

 from that of an ordinary droplet of water. Thus we are dealing with a cell 

 which consists of a cell membrane containing a watery suspension of a 

 number of granules. There is little in either the chemical or physical make-up 

 of an egg cell that distinguishes it from other cells. Indeed, the egg is 

 deceptively simple in appearance compared with a nerve cell. There is 

 nothing which we can see that foreshadows the complex structure of the 

 adult. When we begin to examine the parts of the egg with respect to their 

 abilities to develop into structures, however, we find very striking differences 

 between the different regions of the egg. 



Before beginning with the analysis of our problem we may visualize two 

 possibilities with respect to the organization of an egg. Either each organ in 



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