ORIGINS OF AGAMIC PATTERNS 643 



that in Polyspondylium in that pattern results from directed growth of 

 individual axes instead of directed movement and aggregation of individ- 

 ual cells, but in both cases pattern originates in the common reaction of 

 individual cells to some factor or factors in their environment. 



CONCLUSION 



It should be evident from this chapter that the problems of pattern 

 in development are not limited either to embryonic development or to 

 fissions, buds, and reconstitutions. While there are various types of de- 

 velopment about which we know little or nothing, the evidence from ob- 

 servation points, in general, in the same direction as the experimental 

 evidence in indicating that in some, if not in all of these, developmental 

 pattern is a reaction of a specific protoplasm to factors in its environment 

 within a parent organism or external to it and that pattern is primarily 

 dynamic in character rather than structural. Moreover, development of 

 a definite and orderly axiate pattern from directed motor reactions and 

 aggregation of primarily separate, amoeboid cells, from a multitude 

 of diatoms in a jelly-like secretion, and by directed growth reactions of 

 fungus hyphae suggests, like the experimental evidence from cell aggre- 

 gates, buds, and reconstitutions, that axiate organismic pattern is, or 

 may be, something different from the primary pattern of the cell or of a 

 protoplasm, often on a larger scale, and superimposed from without. But 

 whatever the initiating factor or factors, the character of development 

 within the pattern depends on the specific constitution of the protoplasm 

 concerned. Axiate pattern in the aggregates of Polyspondylium myxamoe- 

 bae develops as Polyspondylium; in an aggregate of Corymorpha cells, as 

 Corymorpha; and in a spermatid of a particular species, as a spermatozoon 

 of that species. 



