January 12, 1922] 



NATURE 



35 



Acquaintance with the Greek spirit through such 

 jans is much needed in science teaching when the 

 je is reached at which a student can appreciate 

 le systematising aspects of science. Early interest 

 science comes through wonder and delight in the 

 itrinsic beauty and charm of natural phenomena, 

 id is followed by interest in the use of the forces 

 ii Nature by man. With adolescence comes the 

 )wer of appreciating systems of theoretical com- 

 )leteness and unity, and it is then that attention 

 lay usefully be turned to the thoughts of Greek 

 lilosophers. Young pupils are very rarely im- 

 liressed by unifying principles and philosophical 

 seculations whether placed before them in Greek 

 their own language. Their work in science is 

 lius almost necessarily limited to acquaintance with 

 perceptual phenomena, and conceptual ideas make 

 little appeal to them. Similarly in historical studies 

 striking episodes and dramatic events are more 

 easily intelligible to immature minds than the con- 

 stitutional or other causes which produce them. 

 Probably a grammatical generalisation is more 

 readily understood than a principle derived from 

 laboratory measurements, and on that account pupils 

 who have been trained to apply scientific method 

 to language may be better prepared to take up the 

 study of science seriously than one in whose mind 

 there is nothing but loose ends. Whether Greek and 

 Latin are essentially the most suitable languages 

 for promoting this sense of law and order, as well 

 as facility in the art of expression, is a matter of 

 opinion. There may on these grounds be a value 

 in preliminary training in classics to students who 

 propose to devote themselves mainly to scientific 

 pursuits, but there is so much in Greek science and 

 philosophy that cannot be understood without 

 acquaintance with natural knowledge that an even 

 stronger plea can be made for training in science 

 for those who intend to give their chief attention 

 to classical studies. 



The Hormone Theory of Heredity. 



Hormones and Heredity: A Discussion of the 

 Evolution of Adaptations and the Evolution of 

 Species. By Dr. J. T. Cunningham. Pp. xx-f 

 246 + 3 plates. (London: Constable and Co., 

 Ltd., 1921.) 245. 



IT would be no exaggeration to say that holes 

 could be picked in any theory of heredity as 

 yet put forward. The problem is one of great diffi- 

 culty and complexity, and when we think of the 

 enormous number of qualities or " factors " con- 

 veyed in the minute space of an ovum, or still more 

 in a single sperm-cell, it seems at first sight im- 

 NO. 2724, VOL. 109] 



possible to believe that all these qualities are " re- 

 presented," rather than that the presence of certain 

 of them, which might be called "key-factors," 

 imply the development of numerous others. But, 

 however this may be, the thought suggests itself 

 that perhaps the knowledge we possess of the nature 

 of protoplasmic structure and function is not yet 

 sufficiently advanced to warrant the statement of 

 any theory professing to be adequate. We are, 

 indeed, in some doubt even with respect to certain 

 fundamental facts. As will have been clear to 

 readers of the correspondence in these columns, in 

 which Sir Archdall Reid and others have taken part, 

 the actual meaning of many of the terms used is in 

 dispute. 



It may be of use to attempt to express in a few 

 words the main question at issue without using 

 language of uncertain connotation. Suppose, then, 

 that an organism is exposed to a new set of external 

 conditions. Some forces or influences acting upon 

 it are changed, and the effects produced in the 

 organism, which we call its " reactions," are not 

 the same as before. These reactions are, of course, 

 conditioned by the nature of the organism itself, and 

 may or may not be of such a kind as to be of benefit 

 to it in adjustment to the new state of affairs. If 

 they are so, they are sometimes called " adapta- 

 tions." But this term is apt to suggest to certain 

 minds a species of directing agency, and is best 

 avoided. In any case, the length of life of such an 

 organism will be dependent on its response to the 

 changed conditions. Those organisms with the 

 longer life naturally leave more ofi"spring, which 

 will be more like their parents than like the off- 

 spring of parents which have responded less favour- 

 ably to the change in environment. The first-men- 

 tioned ofi"spring will, therefore, respond to this 

 changed environment in the same way as did their 

 parents, and probably some of them, owing to the 

 random shuffling of the material of the germ-cells, 

 more favourably. 



It will be seen that we are not justified in speak- 

 ing of such a case as one of " inheritance of 

 acquired characters." If the response in question 

 were continued in the offspring after the altered 

 environment had returned to its original or some 

 other state, an alteration in the "germ-plasm " 

 might be supposed to have been produced. But 

 some difficulty arises here in respect of cases in 

 which it appears that a change may be persistent 

 for a few generations and that then reversion to the 

 original mode may occur. Are such cases to be 

 regarded as changes brought about in the germ- 

 plasm ? We note how difficult investigation is made 

 by the length of time needed for the tests. Many 

 researches are in progress at the present time, and 



