November 26, 1908] 



NA TURE 



" hundred god," and to the local deities of hill and 

 river, the flesh being consumed only by the men, who 

 must live apart from their wives during the rites; 

 the cremation of the dead with subsequent interment 

 of the bones, the ceremonies including an elaborate 

 animal sacrifice and a tribal dance; the bachelors' 

 club of youths associated for agricultural work, 

 which is now passing into decay. Among the 

 Meitheis may be noted the selection of a man w-ho 

 gives his name to the year, bears all the sins of 

 the people during that period, and whose luck, for 

 good or ill, influences the luck of the whole country. 

 Sportsmen will be interested in the account of polo, 

 with its primitive regulations. Introduced into Mani- 

 pur from the Indo-Tibetan region about 1600 a.d., 

 the possibilities of the game were suggested to 

 British ofl'icers by Manipur teams which played at 

 Cachar and Calcutta. 



SOME SCIENTIFIC CENTRES. 

 No. XIV. — The Hortus Botanicus at Amsterdam. 



THE name of one of the most famous centres in 

 the domain of biology conveys little idea of 

 what goes on there to the average English-speaking 

 man, unless he knows already. The Experimental 

 Garden — as this centre is called — in the Hortus 

 Botanicus at Amsterdam is a laboratory in which the 

 results for which it is famous have been obtained, not 

 bv e.xperiment, but by observation, as we usually 

 understand these terms. 



This is not the place to discuss the question whether 

 a line can be drawn between experiment and observ- 

 ation ; nor, supposing that one can, to attempt to 

 arrive at some conclusion as to where observation 

 ends and experiment begins. But it seems to us 

 that the whole essence and significance of de Vries's 

 work lies in the fact that it has been a work of 

 observation. De Vries's name will be remembered as 

 that of the man who saw what Darwin foresaw ; 

 who spent his life in carefully observing and accu- 

 ratclv recording the process of the origin of species. 



To appreciate the nature of the work which has 

 been done in the Experimental Garden, it is neces- 

 sary to take a brief glance at the main features of 

 the previous attempts to deal with a problem which, 

 until de Vries attacked it, resisted all attempts to 

 solve it satisfactorily. This survey will also serve to 

 cxpl.-.in more fully what is meant by the statement 

 ihat de \"ries's work was, in the main, one of observ- 

 .ition. 



The history of the efforts of biologists to deal with 

 the problem of evolution, as told by de Vries in his 

 " Mutationstheorie," is a history of the gradual 

 improvement of the power of observation, which first 

 saw in the genera the units of the natural system ; 

 then the Linnean species ; and, finally, the elementarv 

 species of which the Linnean species are composed. 

 .-Xt each stage in this history, the observer very 

 naturally regarded as the ultimate unit of the natural 

 system that unit which he saw by focussing his 

 facultv of observation on it as finely as he could. 

 In pre-Linnean days, the genera were regarded as the 

 units; from then until now, the Linnean species have 

 been so regarded, and the modern view, put forward 

 bv de Vries, is that the Linnean species are compound 

 things, being, in fact, composed of the elementarv 

 species, which arc the real units of the natural 

 ^vstem. 



In pre-Lamarckian days, the chief attribute of the 

 real imit of the natural system was that it had been 

 created, and had not arisen bv natural means. So 

 that when Linnaeus elevated the species to the rank 



NO. 2039, VOL. 79] 



of the unit of the natural system they acquired this 

 attribute automatically. Species tot numeramus quod 

 diversae forinae in priticipio sunt creatae are Linnaeus's 

 words. It is a very interesting fact that Linnaeus 

 knew that his species were capable of further sub- 

 division into what he called varietates minorcs ; but 

 these had arisen by natural means, and so were not 

 worthy of the attention of the serious student. 

 Varietates levissinias non curet botanicus were the 

 words in which he forbade his students to pay any 

 attention to them. The fads of genius are not buried 

 w-ith their authors. Prof, de Vries himself can 

 remember pointing out on one or two occasions, when 

 a student, curious abnormalities and instances of 

 apparent subspecific characters to his professor, and 

 being told by him not to pay any attention to them. 

 He has occupied the rest of his life in doing so. 



The nucleus of the Experimental Garden at .Amster- 

 dam was a certain potato-field near Hilversum, not 

 far from Amsterdam. It had been bounded on its 

 southern side by a canal from time immemorial. In 

 1870 the owner of the field, Mr. Six, had an extension 

 of the canal dug along its western and part of its 

 northern side ; the result of which was that the 

 original access to the field on its northern border was 

 blocked, and that it could only be reached by its 

 eastern side, where, however, there was, unfor- 

 tunately, no road. Mr. Six found himself unable to let 

 the field, and decided to plant it with trees. Rough 

 paths were accordingly cut, and small trees planted. 



Here was a wonderful opportunity for the wild 

 plants, which had been kept in check with the hoe 

 year after year, to establish themselves and multiply 

 — an opportunity for the supercession of the horticul- 

 tural by the cosmic process, to borrow Huxley's 

 famous illustration. Vet, curiously enough, the 

 fullest advantage of this opportunity was taken, not 

 by an indigenous species, but by an introduced one 

 which had spread over into the field from a small 

 bed in a park close by, where a few annuals were 

 grown every year. It was the beautiful evening prim- 

 rose, CEnothera Lamarckiana. 



De Vries first saw the field in 1886. The CEnotheras 

 spread over a wide zone, the centre of radiation of which 

 was the point at which the species had invaded the 

 field. The centre of this zone was covered by a dense 

 jungle of CEnotheras as tall as a man ; outside this 

 zone the adult plants gradually gave way to younger 

 ones, whilst outside of all was an advanced guard 

 of rosettes which did not lift their heads above the 

 level of the ground. 



.iVll this seemed to offer to de Vries an opportunity 

 which might never occur again of studying the 

 phenomena of variation as exhibited by a plant mul- 

 tiplying, practically without restriction, in a state of 

 nature. • Moreover, he had been trying for some 

 vears past to find plants in a state of mutation (that 

 is, of giving off new elementary species) but in vain. 

 CEnothera broke the spell of failure. It was in a 

 mutable period ; new elementary species were aris- 

 ing; two had already arisen in the potato-field, 

 CEnothera hrcvistvlis and (TT. laevifolia. It verv soon 

 became evident that, to observe the process of the 

 origin of mutations properly, it was necessary to grow 

 the plants under direct personal observation in one's 

 own garden. In the first place, only a very small 

 proportion of the seeds that are shed in nature can 

 germinate, and, of those that do, a verv small pronor- 

 tion can attain maturity; so that if a mutation does 

 arise the chance that the seed which contains it will 

 survive to maturitv is small. In the second place it 

 is impossible to know the parentage of any of the 

 plants in the field, partly because it is not possible to 

 know from which plants the seeds which gave rise to 



