Origin of Species Variorum

to the great central ganglion of an insect would have been variable in the same species; it might have been thought that changes of this nature could have been effected only by slow degrees; yet recently Sir J. Lubbock has shown a degree of variability in these main nerves in Coccus, which may almost be compared to the irregular branching of the stem of a tree. This philosophical naturalist, I may add, has also recently shown that the muscles in the larvæ of certain insects are .. far from uniform. Authors sometimes argue in a circle when they state that important organs never vary; for these same authors practically rank those parts as important (as some few naturalists have honestly confessed) which do not vary; and, under this point of view, no instance will ever be found of an important part varying: but under any other point of view many instances assuredly can be given.

There is one point connected with individual differences, which is extremely perplexing: I refer to those genera which have .. been called "protean" or "polymorphic," in which the species present an inordinate amount of variation; and about which hardly two naturalists .. agree whether to rank them as species or as varieties. ↑ We may instance Rubus, Rosa, and Hieracium amongst plants, several genera of insects, several genera of Brachiopod shells, and the Ruff (Machetes pugnax) amongst birds. In most polymorphic genera some of the species have fixed and definite characters. Genera which are polymorphic in one country seem to be, with some few exceptions, polymorphic in other countries, and likewise, judging from Brachiopod shells, at former periods of time. These facts are very perplexing, for they seem to show that this kind of variability is independent of the conditions of life. I am inclined to suspect that we have at least in some of these polymorphic genera variations