988 LIFE : OUTLINES OF GENERAL BIOLOGY 



forms with reflexed shell-valves such as their parents had acquired. 

 Later on, however, when the parents laid again the abnormal effect 

 was seen only to a very slight degree, and in a third brood it had 

 dwindled away. The probability is that the abnormal nurture 

 resulted not in any disturbance of the inheritance, but in the 

 formation of some peculiar non-living metabolic product, which 

 was included in the cytoplasm of the egg, passed passively 

 into the body which developed from the egg, and there produced 

 on the body of the offspring the same effect as it originally pro- 

 duced on the body of the parent which acquired the character 

 in question. 



In this connection reference may be made to a view sketched by 

 an ingenious French biologist, Bohn. In one aspect the organism 

 is a vast system of correlated chemical processes. There are numerous 

 main lines of metabolism which work together. If conditions demand 

 it, there may be a great local increase along any one of these lines, 

 just as in the activities of a country. Thus, hard exercise of the 

 limbs may induce unusually intense myogenic metabolism — the 

 development of muscle substance. This is seen in the professional 

 dancer, for instance. But because of correlation — a fact imperfectly 

 understood — the myogenic fashion, so to speak, spreads, and affects 

 other parts of the body, such as the dancer's heart. Now it may be 

 that although the germ-cells remain unaffected by any particular 

 muscular modification, they may be specifically affected by a general 

 dominance of myogenic metabolism. 



Very striking and suggestive are Child's experiments on the effect 

 of altered diet on Planarian worms. Thus a diet of freshwater 

 mussel depresses the vitality, i.e. lessens the rate of metabolism and 

 the power of resistance. The stock becomes senescent, and if the diet 

 be continued for several generations there is an aggravation of 

 senescence, for they begin to be bom old. The effect of the mussel 

 diet is cumulative. One does not thereby argue from worm to man, 

 but one recognises the importance of competent experiments which 

 show that the course of the life-cycle may be greatly altered by 

 changing the character of the food. 



Bordage made some interesting observations on European 

 peach-trees transported to Reunion. As has been noticed in similar 

 cases, they dropped their deciduous habit and became — it took some 

 of them twenty years — evergreen. The individual constitution was 

 altered. Still more interesting was the fact that when seeds of these 

 neo-evergreens were sown in certain mountainous districts with a 

 considerable amount of frost, they produced young peach-trees 

 which were also evergreen. European seeds sown in similar places 

 produced ordinary deciduous trees. Yet it is possible that the 

 apparent inheritance in the case of the evergreen peach-trees was 

 the result of an influence on the body of the seed before it was 



