I] CHEMICAL EMBRYOLOGY 15 



use Lloyd Morgan's terminology — a physiological tale cannot be told 

 separately from a psychological tale. Instead of expressing living 

 processes in terms of physical causes and effects, the hormists wish 

 to regard unconscious striving as the essential urge in life, and such 

 conceptions as food, rest, fatigue, etc., as irreducible biological cate- 

 gories. These thinkers do not often acknowledge their debt to Galen 

 of Pergamos, who put forward, as early as a.d. 170, an essentially 

 similar conception as the basis of his biology. In the treatise On the 

 Natural Faculties he says, "The cause of an activity I term a faculty.... 

 Thus we say that there exists in the veins a blood-making faculty, 

 as also a digestive faculty in the stomach, a pulsatile faculty in the 

 heart, and in each of the other parts a special faculty corresponding 

 to the function or activity of that part". He also said, "We call it 

 a faculty so long as we are ignorant of the cause which is operating", 

 but he never actually suggested any such underlying cause, and 

 seems to have thought it impossible to ascertain. So do the hormists. 

 According to them the actions of protozoa are to be described in 

 terms of avoiding responses, seeking responses and the like, language 

 which, as they claim, is much simpler than the complex terminology 

 of surface tension and molecular orientation. Everything, of course, 

 depends on what is meant by simple. To say that a protozoon seeks 

 the light is evidently more naive than to say that a dimolecular 

 photochemical reaction takes place in its protoplasm leading to an 

 increase of lactic acid or what not on the stimulated side, but since 

 the latter explanation fits into the body of scientific fact known 

 already it is open to the biochemist to say that, for his part, he. con- 

 siders the latter explanation the simpler. It is, in fact, simpler in 

 the long run. Psychobiology or hormism differs from the other 

 forms of neo-vitalism because it insists on retaining " commonsense " 

 explanations in biology as categories of biological thought beneath 

 which it is impossible to go. It dismisses the entelechy of dynamic 

 Teleology, on the ground that it acts, as it were, in addition to the 

 mechanistic schema, accepting the latter fully but interfering in it. 

 It resembles much more finaUsm and organicism, but lays stress 

 rather on the unconscious striving force which seems to animate 

 colloidal solutions of carbohydrates, fats, and proteins. It resembles 

 the Behaviourism of J. B. Watson superficially by emphasising animal 

 behaviour, but it fundamentally differs, for it asks the question — Does 

 an animal see the green light and the red light in this experiment 



