162 



lus aquatilis and Ranunculus circinatus. Many more are deemed va- 

 rieties by the majority, while the minority (one, two, three, or more) 

 describe them to be species ; as Alchemilla alpina and Alchemilla 

 conjuncta. 



The step from those plants which are allowed by all to be simply 

 varieties, into others which only very few botanists (perhaps only a sin- 

 gle botanist) suppose to be distinct species, must be a very small step 

 indeed. And once among these dubious species, we may ascend, step 

 by step, from the least to the most generally admitted. A single step 

 more, and we arrive at the universally admitted species. At which, 

 of all these little steps, are we to find the impassable barrier between 

 varieties and species ? Where does the possibility of transition cease, 

 and the impossibility succeed ? 



Notwithstanding a mere theoretical definition, never really applied 

 by way of test to one species in a thousand, the assumed difference 

 between species and varieties, the capability or incapability of transi- 

 tion, is simply conjectural — an unproved idea of the mind — a.petitio 

 principii. The assumption is so far a safe one, that it never can be 

 disproved, never can be put to a test which would be conceded by its 

 believers. Could any one raise a beech tree from the acorn of an oak, 

 the botanists might fall back on their theoretical definition, and argue 

 that the fact only proved the beech and oak to be varieties of one sin- 

 gle species. While the transitionist, on the other hand, would feel 

 himself entitled to put forward the fact as a confirmation of his views; 

 namely, that one species could give origin to another different species. 



No doubt so wide a transition as that of an oak into a beech, were 

 it possible, would shake the faith even of the most unreasoning bota- 

 nist. But it is equally an arbitrary assumption on the part of botanists, 

 to say that a cowslip and primrose are proved varieties of a single 

 species, if one can be raised from the seeds of the other. The dis- 

 tinction is one of degree only ; the oak and beech being more dissi- 

 milar, the cowslip and primrose less dissimilar. 



Still, the tendency of like to produce like, is so evident and decided 

 throughout the best understood operations of Nature, that botanists 

 may reasonably call on the transitionist to prove, if he can, that the 

 exceptions to this tendency may extend so far as species. On the 

 other side, the transitionist may plead that he should not be required 

 to show cases of change between very dissimilar species ; but that he 

 creates a presumption in favour of his views, when he adduces instan- 

 ces of transition in plants which are held to be distinct species by 

 botanists of acknowledged skill and reputation. 



