Some Questions ivhich they Suggest. 33 



by those of its own kind, and of remaining indifferent and 

 neutral towards those of other kinds. 



That the pollen of an oak should not act on a daisy 

 seems to us natural ; that the naked protoplasm of these 

 minute organisms should be endowed with this selective 

 capacity does seem very remarkable, and may well make 

 one pause and think. Is it possible, one inclines to ask, 

 to feel sure that all the various species of myxies have been 

 produced from one original form by the force of a natural 

 selection ? How can the doctrine of the fittest be applied 

 as between two naked protoplasts, and if applied only to 

 the later stages of growth, how has it reacted on the earlier 

 stages ? 



CLASSIFICATION. We now propose to deal with the classi- 

 fication of these organisms, and this will afford us an 

 opportunity of describing more in detail some parts of their 

 structure. 



The value of characters for the purposes of generic and 

 specific distinctions is a subject well worth consideration, 

 for it often reveals unexpected facts in the correlation of 

 parts, startling one by dividing organisms which, at 

 first sight, seem nearly akin. Colour is for the most part 

 of little value as a distinction in flowering plants, for 

 we know how widely colour will vary in the same species. 

 " Color," says Linnaeus, " in eadem specie mire ludit : hinc 

 in differentia nil valet;" and yet in the pimpernel, the blue 

 and red forms differing in scarcely any other character are 

 true and not interchangeable species ; in the algae the 

 presence of colours other than green is found a funda- 



