286 



[December 13, 191 7 



domestic animals and cultivated plants (and of 

 man himself) is to some extent controllable, be- 

 cause we can by selection influence the variability 

 of later generations ; according to De Vries, evolu- 

 tion is beyond our control except as we discover 

 and isolate variations. Thus does Prof. Castle 

 contrast the two sets of. views, which " remind us 

 somewhat of the theological ideas of free-will and 

 predestination respectively." But which view is 

 right? 



The evidence from palaeontology, geographical 

 distribution, and classification tends on the whole 

 in favour of the Darwinian view that " evolution 

 as an age-long process has been gradual and pro- 

 gressive, not abrupt and unguided," but the evi- 

 dence from experimental breeding leans to either 

 side. The mutationists hold that selection "can 

 do nothing but isolate variations which may 

 sporadically put in an appearance or which may 

 by hybridisation be brought together into new 

 combinations." The selectionists, with whom 

 Prof. Castle ranks himself, maintain that selection 

 "can accomplish more than the mere isolation of 

 variations, because it can, by a series of selections, 

 influence further variability." How is one to 

 decide? 



Prof. Castle considers carefully the attempts that 

 have been made to generalise Johannsen's brilliant 

 discovery of the principle of "pure lines," and 

 shows that this is not warranted. In the case of 

 certain- characters in guinea-pigs he has himself 

 found that a ne plus ultra is reached which 

 cannot be changed by selection in an inbred race. 

 "Thus a very dark form of Himalayan albino, 

 after a certain amount of improvement 

 by selection, could not be further darkened 

 to any appreciable extent." On the other 

 hand, certain characters of guinea-pigs, 

 rabbits, and rats have been found to respond 

 readily to selection in a particular direction. Prof. 

 Castle's experiment with hooded rats " selected 

 simultaneously in plus and minus directions has 

 produced one race which is black all over except a 

 white patch of variable size underneath, and 

 another race which is white all over except for the 

 top of the head and the back of the neck, whioh 

 are black. The races do not overlap at all, and 

 have not done so for many generations, though 

 they still continue to diverge from each other as 

 a result of continued selection " 



It comes to this, that divergent conclusions are 

 in part due to the data utilised. 



"A study of albinism alone would lead one to believe 

 in the fixity and constancy of Mendelian genes and 

 the impossibility of modifying them by selection." 

 But " in the case of such characters as white spotting 

 in mammals, it is evident that a change in the mean 

 of the character In a particular direction in consequence 

 of selection actually displaces in the direction of selec- 

 tion the centre of gravity of variation, so that In a 

 very true sense selection makes possible further varia- 

 tion In that same direction." 



Selection cannot start new lines of variation, but 

 it can continue and extend variation already 

 initiated. J. A. T. 



NO. 251 1, VOL. 100] 



THE FUTURE OF THE TRADE IN 

 COLONIAL RAW MATERIALS. 



IT is now well known that before the war large 

 quantities of raw materials produced in the 

 British Colonies found their way in the first in- 

 stance to Germany, where they were converted 

 into manufactured products, of which considerable 

 quantities were then exported from Germany to 

 this country and other parts of the Empire. Most 

 people are now of opinion that this indirect method 

 of trading should not be resumed after the war, 

 and that these intermediate processes of manu- 

 facture should be carried on in this country, or at 

 least within the Empire. It has also become 

 clear, especially in the last few months, that 

 immediately after the war there will be great com- 

 petition among all the manufacturing countries for 

 supplies of raw materials, and probably most 

 people in the Allied countries, who realise that 

 the Allies effectively control the bulk of the world's 

 supplies of such materials, are of opinion that the 

 Allies should utilise this advantage to meet their 

 own requirements first. 



There can be little doubt as to the trend of 

 pubhc opinion on these points, but it is not at "all 

 clear what action, if any, is being taken to give 

 effect to it, except in the one case of West African 

 oil-seeds, which was investigated by a special com- 

 mittee appointed by the Colonial Office in 191 5. 

 That committee recommended the imposition of 

 an export duty on palm kernels exported from 

 British West Africa to be crushed in countries 

 outside the Empire, and this recommendation was 

 adopted by the Secretary of State for the Colonies, 

 with the result that the palm-kernel crushing in- 

 dustry established in this country since the war 

 is likely to remain here in future. The publica- | 

 tion of the results of the British committee's in- i 

 vestigations has apparently stimulated the * 

 Colonial Institute at Marseilles into conducting 

 similar inquiries into the sources of supply of the 

 raw materials which form the basis of two of 

 the chief industries carried on in Marseilles, 

 namely, oil-seeds and cereals. 



Committees have been appointed by the Mar- 

 seilles Colonial Institute to investigate these two 

 groups of raw materials, and the Oil-seeds Com- 

 mittee has already published two special bul- 

 letins. The first of these contains the report (in 

 French) of the British West African Oil-seeds 

 Committee, and the second gives a risume of 

 some of the evidence taken by that committee, 

 a translation of a portion of the Imperial Institute 

 monograph on oil-seeds and feeding-cakes 

 (Murray, 1915), and some preliminary information 

 regarding the work of the French committee. 

 The latter is first taking up questions connected 

 with the trade in ground nuts, the most important 

 oil-seed crushed in Marseilles ; and the bulletin 

 contains evidence for and against the decortica- 

 tion of ground nuts before shipment, a matter of 

 first-rate importance in connection with the 

 ground-nut trade of India. Hitherto, it has been 

 held that ground-nut oil of edible quality cannot 



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