176 



MORPHOLOGICAL DEVELOPMENT. 



irregular in the interior e, where there is no definiteness in 

 the conditions to which they are exposed. Thus the diver- 

 gences of these cells from primordial sphericity are such as 

 correspond with unlikenesses in their circumstances. And 

 throughout the more complex modifications which the cells 

 of other tissues exhibit, the like correspondences hold. 



Among plants of a lower order of aggregation, we have 

 already seen how cells become metamorphosed as they become 

 integrated into masses having definite organizations. The 

 higher Algce, exemplified in Figs. 32, 34, 35, show this very 



clearly. Here the departure from 

 the simple cell-form to the form 

 of an elongated prism, is mani- 

 festly subordinated to the con- 

 trasts in the relations of the 

 parts. And it is interesting to ob- 

 serve how, in one of the branches 

 of Fig. 32, we pass from the small, 

 almost-spherical cells which ter- 

 minate the branchlets, to the 

 large, much-modified cells which 

 join the main stem, through gra- 

 dations obviously related in their changed forms to the 

 altered actions their positions expose them to. 



More simply, but quite as conclusively, do the inferior 



Algce, of which Figs. 19 — 23 are examples, show us how 



J9 



cells pass from their original spherical symmetry into radial 

 symmetry, as they pass from a state in which they are simi- 



