OBJECTIONS TO THEORY OF DETERMINANTS 451 



to dispense with the concept of " units," or " primary constitu- 

 ents " or " determinants " or groups of these including all the 

 specific characters. Take the case of the common Infusorian 

 Stentor. It seems to be certain that a thin slice, a millimetre 

 thick, of this unicellular organism may, in appropriate con- 

 ditions, grow into a complete individual, with vibratile oral 

 cilia, smaller superficial cilia, a mouth, a long necklace-like 

 nucleus, three smaller nuclei, a contractile vacuole, internal 

 contractile fibrils, and so on. Is it possible to think of this 

 marvellous regeneration of a highly differentiated unity from a 

 thinsHce, without postulating " units " of some sort, which, when 

 removed from the system as a whole, have yet the power of 

 reconstituting that system ? (See Weldon, 1905, p. 42.) Simi- 

 larly, a thin slice of the multicellular Hydra-polyp may, in ap- 

 propriate conditions, grow into an entire and complete Hydra. 

 Is it possible to conceive of this apart from the postulate of 

 diffusely distributed " specific units " ? 



Prof. H. E. Ziegler has briefly and temperately stated the 

 two most frequent objections to the theory of representative 

 particles. 



I. When we try to interpret any result or occurrence we 

 must refer it to what is known. If we interpret it in terms 

 of a something invented for the purpose we are simply making 

 a fictitious hypothesis. When we refer facts of inheritance to 

 observable processes — e.g. in the chromosomes of the nuclei — 

 we are making scientific progress ; but when we deduce the 

 phenomena of inheritance from the behaviour of pangens or 

 determinants which have been invented we are simply indulging 

 in verbal speculation. As it appears to us^ this is not a just 

 statement of scientific procedure. The imaginary pangens or 

 determinants are elements in a notation like the graphic symbols 

 of chemical molecules : their utility does not depend on any 

 visible reality ; their validity is tested by the degree in which 

 they enable us to formulate conceptually what does occur, and 



