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SEX-LORE 



at different rates, so that at the end a structure arises 

 very much like an indiarubber ball completely bulged 

 in. It forms a double hemisphere of cells called the 

 gastrula, and consists of an outer layer and an inner 



Fro. 35. EMBRYOGENY OP SAGITTA. 



1 to 4, Primitive mother-cell with successive divisions ; 5, morula ; 

 0, blastula ; 7 and 8, gastrula ; 9 and 10, ccelomula ; e, outer 

 layer ; i, inner layer ; o, primitive mouth ; a, primitive mouth- 

 or gut-cavity ; v, coslom folds ; c, crelom cavity. 



(From " Natural History of Creation," by E. Haeckel. By kind permission of the 

 Author and Publisher.) 



layer of cells. This double layer of cells encloses a 

 cavity which opens outwardly. The next stage 

 consists in an elongation of the gastrula into horse- 



