A4 PATTEN. [Vor. XII. 
a flat, instead of aspherical surface, — we should have a succes. 
sion of organs like that in the lower half of Figs. 1 and 2. But 
each half-metamere not only grows in length but in width, 






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Fic. 4. 
Diagrams to illustrate how a double series of half-metameres formed in succession from before 
backwards, and growing on a spherical surface, will produce differential growth forces. 
These in turn produce median concrescence and degeneration, cervical and caudal flexures, 
and the modification of the trunk into regions of different morphological and physiological 
potentialities. 
and as this is most manifest at the lateral end, they will tend 
to be triangular inform. Moreover, each succeeding metamere 
will have to grow under other conditions of cell tension and 
available yolk surface than the metamere that preceded it. 
a 
