172 DEVELOPMENT AND HEREDITY. 



thing illustrated in other animals. Many worms may 

 be divided into a number of parts, each of which will 

 grow again into a complete individual. The Hydra 

 may be chopped to small bits, and the pieces will 

 develop into an indefinite number of Hydras. There 

 are some conclusions to be drawn from these phe- 

 nomena ; namely, the co-ordination of forces, which 

 determines development, is not to be regarded as a 

 definite, localised mechanism, wound up and ready to 

 go when touched. If such were the case, we ought 

 to find one such mechanism allotted to a certain defi- 

 nite number of cells ; but, instead, we find that each 

 piece, regardless of the number of cells, or whether 

 it be the half or the twentieth of the Hydra, is capa- 

 ble of producing only one new individual. The 

 power of living matter to produce new individuals 

 is dependent, therefore, not on the quantity of that 

 matter nor, apparently, upon the unfolding of any 

 limited mechanical arrangement of latent energy. 

 The quality upon which development depends seems 

 to reside in a small piece as well as in a large piece, 

 and, moreover, equally in all parts. How this may 

 be, it is not easy to conceive and much less easy to 

 express. I think we can best compare the inherence 

 of the plan and potentiality of development in the 

 clump of protoplasm to inherence of ideas and po- 

 tentialities of volition in the brain substance, not as 



