348 



PATTERNS AND PROBLEMS OF DEVELOPMENT 



in Corymorpha by contact with the glass of the container or by low oxygen 

 provided in some other way. 



Differences in scale in development of aggregates of dissociated cells 

 from Corymorpha stems are also extreme, not only with size of aggregate 

 but with external conditions (Child, 1928c). Aggregates remaining un- 

 disturbed in contact with a glass surface usually (79 per cent) develop 

 apical ends from the free surface and a base from the surface in contact 

 and become either completed individuals or "mosaic" forms, consisting 



Fig. 118, A-D. — Corymorpha. Aggregates of dissociated cells moved about and turned over 

 from time to time (from Child, 1928c). 



of apical and basal parts without intervening regions. The range of dif- 

 ference in scale in such forms with difference in size of aggregate is indi- 

 cated in Figure 117, A-D. Aggregates frequently moved about and turned 

 over develop predominantly unipolar or bipolar apical parts of hydranths 

 on a much larger scale (Fig. 118, A-D). There is no question as to the 

 capacity of these stem pieces and aggregates to give rise to complete in- 

 dividuals. What actually develops in any particular case depends on scale 

 of organization, as determined by physiological and external conditions. 

 It is evident that scale of organization determined in a piece may greatly 

 exceed length of piece, or in cell aggregates, size of aggregate, or in bipolar 

 and multipolar forms, length to which each axis can develop. Each gra- 



