OBSERVABLE PROPERTIES OF EACH SPECIES 19 



Hypericum perforatum, etc. I was again and again brought 

 to the conclusion that the species under natural conditions 

 are on the whole more variable than we are tempted to 

 believe. 



Among wild animals examples of astonishing variation are 

 found as soon as attention is paid to a large number of speci- 

 mens. EXAMPLES (observed in Flanders) : Rana tempo- 

 raria is very variable with regard to its colour. This is also the 

 case with Aphrophora,^ Eristalis tenax,^ Neritina fluviatilis, etc. 

 On the dunes near the Flemish coast (Ostend, Blankenberghe, 

 etc.), on certain hot summer days, Coccinella novemdecim- 

 punctata is found in millions of specimens. If one collects 

 several hundreds of them, places them side by side and observes 

 them with a glass, one is astonished by their diversity. It is, 

 however, very difficult to accept the suggestion that com- 

 plexity is here in play. 



The above examples of variation among animals are rather 

 exceptional. It is incontestable, however, that even in ordinary 

 cases we overlook variation in the state of nature because we 

 almost never compare a sufficient number of specimens. 



The conclusion is that the influence of cultivation and 

 domestication on variation is on the whole less important than 

 we have been told. Many years ago, at a time when our know- 

 ledge of variation was incomplete, attention was called to the 

 variation of cultivated and domesticated species (DARWIN). 

 Ever since, numerous new observations have been made, but 

 the fundamental distinction between complexity and plasticity 

 has been continually overlooked. Preconceived theories 

 (Darwinism, Neo-Lamarckism), combined with the obsession 

 of adaptation, have prevailed too much in the minds of many 

 observers. 



§ 24.— VARIATION UNDER CULTIVATION {continued). 

 PLASTICITY OF MONOTYPIC SPECIES.— When we bring 

 a plant species under cultivation the conditions of existence are 

 more or less modified. They may be less favourable ^ than in 

 the state of nature, or they may be on the whole better, the 

 plants being grown in a manured soil, at sufficient distances 

 fr(5m one another, and watered, and protected against the pre- 

 judicial influence of weeds. The gardener often succeeds, after 

 several fruitless attempts, in finding the best possible conditions. 



^ Here variation depends probably to a considerable extent on the fact that 

 the larvae of Aphr. spumaria live on various species of plants. 



* This species was formerly exceedingly common in Flanders, the larva; 

 being injurious to flax in the rettories (retting-ponds). It has been, like 

 many other flower-visiting insects, almost completely destroyed by the cool, 

 rainy summers of 1909-1910. In 191 1 it was rather a rarity. 



' That is to say, less appropriate to the needs of the species. 



