654 



THE AMERICAN NATURALIST [Vol. LI 



duced in a similar fashion, by removing the region of the 

 embryo from which the germ cells arise.^*' 



The blastoderm is of course detinitely organized, since 

 its cells contain organized cytoplasm, and by killing parts 

 of the eggs in the blastoderm and later stages results 

 were obtained similar to those produced when fresh eggs 

 were operated upon (Fig. 7, h, c, d). 



7. Stmimary of Part I 

 Summarizing the data briefly given above, we may say: 



1. Morphological and experimental studies liave proved 

 that the eggs of animals are more or less highly organ- 

 ized at the time of fertilization. 



2. We know ;iliii()st nothing about the nature and geu- 



3. Desci iptiotis are given of the condition of the eggs 

 of certain clirysomelid beetles at the time of deposition, 

 of. the stages of cleavage and blastoderm formation, of 

 tlie origin of the germ cells, and of the principal stages 

 in the germ-cell cycle. 



4. The egg> of certain chrysomelid beetles and of other 

 inxH'ts are (h^finitely oi-gaJii/ed when de])Osited as indi- 

 cated by observations on noi'nially developing eggs and 

 by experinuMits with gravity. 



5. This oi-ii;ini/ntion exists in the cytoplasm as indi- 

 ratcd a niorphoh)gical study of cleavage, by ex])eri- 

 nicnt> with gravity and centrifugal force, and by killing 

 with a hot needle parts of eggs in various stages of de- 

 Nclopment. 



(5. These observations and experiments prove also that 

 the nuclei u|) to the time of blastoderm formation are 

 totipotent. 



II. Tin: ({knp:sts of tiik Okoaxtza riox of tiik Tnsfct Kcir, 



1 ha\c .Iccidc.l to con-idci' tlic oru-anization of the egg 

 only in thi- di-cu^^inn. -lii<-c il roiitain> everything neces- 



20Eeagan, I'Jlti, .\l-ti:i. t^ U annual in-,.tin- AirifM-. Soo. Zool. 



