120 ON THE ORIGIN OF SPECIES 



susceptible to changes in the conditions of life ; and to 

 this system being functionally disturbed in the parents, 

 I chiefly attribute the varying or plastic condition of 

 the offspring. The male and female sexual elements 

 seem to be affected before that union takes place which 

 is to form a new being. In the case of ' sporting ' 

 plants, the bud, which in its earliest condition does not 

 apparently differ essentially from an ovule, is alone 

 affected. But why, because the reproductive system is 

 disturbed, this or that part should vary more or less, we 

 are profoundly ignorant. Nevertheless, we can here 

 and there dimly catch a faint ray of light, and we 

 may feel sure that there must be some cause for each 

 deviation of structure, however slight. 



How much direct effect difference of climate, food, 

 etc., produces on any being is extremely doubtful. My 

 impression is, that the effect is extremely small in the 

 case of animals, but perhaps rather more in that of 

 plants. We may, at least, safely conclude that such 

 influences cannot have produced the many striking 

 and complex co-adaptations of structure between one 

 organic being and another, which we see everywhere 

 throughout nature. Some little influence may be attri- 

 buted to climate, food, etc. : thus, E. Forbes speaks 

 confidently that shells at their southern limit, and when 

 living in shallow water, are more brightly coloured than 

 those of the same species further north or from greater 

 depths. Gould believes that birds of the same species 

 are more brightly coloured under a clear atmosphere, 

 than when living on islands or near the coast. So with 

 insects, Wollaston is convinced that residence near the 

 sea affects their colours. Moquin-Tandon gives a list 

 of plants which when growing near the sea-shore have 

 their leaves in some degree fleshy, though not elsewhere 

 fleshy. Several other such cases could be given. 



The fact of varieties of one species, when they range 

 into the zone of habitation of other species, often 

 acquiring in a very slight degree some of the characters 

 of such species, accords with our view that species of 

 all kinds are only well-marked and permanent varieties. 



