i894- AN LAG EN. 369 



" middle blasts," would be more logical and not less intelligible than 

 the single term " mesoblast," with its misleading suggestion of homo- 

 geneity. In the case of the other layers, the compositeness of the 

 groups of cells is less obvious, and equally there is less reason to 

 suppose that there could arise any confusion were they to retain 

 the simple designations " epiblast " and "hypoblast," while the word 

 " blast " was used by itself in the sense I now suggest for it. 



P. Chalmers Mitchell. 



2 B 



