THE BIOLOGY OF THE CELL SURFACE 



During development of the egg, all the blastomeres in 

 most cases come to have an equal portion of the ectoplasm. 



The ectoplasm can be traced through cleavage up to the 

 formation of a blastula, but it soon either becomes absorbed 



.^ •••** .»■♦-". 



Fig. 5. — Egg of a sponge, Grantia (after Gatenby) showing amoeboid ectoplasm. 



or is invaded by endoplasmic substance. ... In a rare 

 number of cases, it was found that in young blastulae the 

 cells of one side had less ectoplasm than those elsewhere 

 but in no example could I show that this inequality had 

 any relationship to the formation of the flagellated and 

 non-flagellated parts of the amphiblastula. 





It., i - .-^i.A-^ -. ^-^ >-i >■ v-T ■ •-'■ - ■ ■.■-■■...■■■" ,' -y 



K-i.--.'X< ■ .■ r-r.r,.>.v'.-^,-~.-.i:-- I ■ ■ 



%^^ V■/Vr?A:^..^■••i••■•^<^s^i^■ \ :■:■':: ■■■::'.'.' 



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a i f 



Fig. 6. — Eggs of medusae (after Metschnikoff). a, Liriope mucronata; b, and 



c, Rathkea. 



In the cytoplasm of eggs of all classes of Coelenterates, 

 including the Ctenophores, that is, the jelly fishes and their 

 allies, ecto-endoplasmic differentiation has been frequently 



90 



