62 WITHIN AND WITHOUT 



mnemic theory has been claimed by Rignano in 

 his Scientific Synthesis as a complete explanation, 

 in forgetfulness of the fact that even the all- 

 powerful protozoon can only remember what has 

 passed and could certainly not remember that it 

 was some day going to breed a man. At the mo- 

 ment, things are explained on a chemical basis, 

 though that basis is far from firm ; is of a shifting 

 nature, and a little hazy in details. Some time 

 ago, colloids were the cry. A President of the 

 British Association almost led one to imagine 

 that " the homunculus in the retort " might be 

 expected in a few weeks. But the chemists would 

 have none of this, and denied that the colloids, 

 about which they ought to know more than do 

 the biologists, had that promise in them which 

 had been claimed. We had Leduc and his " fairy 

 flowers," as now we have Loeb and others with 

 their metabolites and hormones. As to these 

 last, there seems to be no kind of doubt that the 

 internal secretions of many organs and structures 

 have effects which were, even a few years ago, 

 quite unsuspected. Those of the thyroid and 

 adrenals are excellent examples. 



It seems to be the fate, however, of all sup- 

 porters of new theories to run into extravagances. 

 Darwin had to remind his enthusiastic disciples 

 that Natural Selection could not create variations, 

 and we may feel some confidence that Hering, 

 were he alive, would urge his followers to bear in 

 mind that memory cannot create a state of affairs 

 which never existed. So far we may certainly 

 say that these internal secretions do produce 



