Origin of Species Variorum

Comparison with 1872

Mr. B. D. Walsh, a distinguished entomologist of the United States, has lately described what he calls Phytophagic varieties and Phytophagic species. Most vegetable-feeding insects live on one kind of plant or on one group of plants; but some feed indiscriminately on many widely distinct kinds, but do not in consequence vary. In several cases, however, insects found living on different plants have been observed by Mr. Walsh to present, either exclusively in their larval or mature state, or in both states, slight, though constant differences in colour, size, or in the nature of their secretions. In some instances the males alone, in other instances both males and females, have been observed to be thus affected in a slight degree. When the differences are rather more strongly marked, and when both sexes and all ages are affected, the forms would be ranked by all entomologists as species. But no man can draw the line for others, even if he can do so for himself, and determine with certainly which of the several phytophagic forms to call varieties and which to call species. Mr. Walsh ranks the forms which it may be supposed would freely intercross together, as varieties; and those which appear to have lost this power, as species. As the difference in all these cases clearly depends on the insects having long fed on perfectly distinct plants, intermediate links between the several forms thus produced cannot be expected to be found; though formerly such must have existed, connecting the present divergent forms with their common progenitor. The naturalist thus loses his best guide in determining whether to rank such doubtful forms as varieties or species. This likewise necessarily occurs with closely allied organisms, of doubtful value, which inhabit separate continents or distant islands. But when an animal or plant ranges over the same continent or inhabits many islands in the same archipelago, and presents different forms in the different areas, there is always a chance, which is not rarely successful, that intermediate forms may be discovered which will link together the extreme states; and these are then degraded to the rank of varieties.

Some few naturalists maintain that animals never present varieties; but then these same naturalists rank the slightest difference as of specific value; and when even the identically same form is met with in two distant countries, or in two distinct geological formations, they go so far as to believe that two separate species are hidden under the same dress. The term species thus comes to be a mere useless mental abstraction, implying and assuming a separate act of creation. It cannot, however, be disputed that many forms, considered by highly-competent judges as varieties, have so perfectly the character of species that they have been ranked by other highly-competent judges as good and true species. But to discuss whether such slightly different forms are rightly called species or varieties, before any definition of these terms has been generally accepted, is vainly to beat the air.

Text in this page (from paragraph 700, sentence 110 to paragraph 700, sentence 300, word 51) is not present in 1872

be ranked as distinct species by many entomologists. Even Ireland has a few animals, now generally regarded as varieties, but which have been ranked as species by some zoologists. Several most experienced ornithologists consider our British red grouse as only a strongly-marked race of a Norwegian species, whereas the greater number rank it as an undoubted species peculiar to Great Britain. A wide distance between the homes of two doubtful forms leads many naturalists to rank both as distinct species; but what distance, it has been well asked, will suffice? if that between America and Europe is ample, will that between the Continent and the Azores, or Madeira, or the Canaries, or Ireland, be sufficient? ↑ It must be admitted that many forms, considered by highly-competent judges as varieties, have so perfectly the character of species that they are ranked by other highly competent judges as good and true species. But to discuss whether they are rightly called species or varieties, before any definition of these terms has been generally accepted, is vainly to beat the air.

Many of the cases of strongly-marked varieties or doubtful species well deserve consideration; for several interesting lines of argument, from geographical distribution, analogical variation, hybridism, &c., have been brought to bear on the attempt to determine their rank. I will here give only a single instance,— the well-known one of the primrose and cowslip, or Primula veris and elatior. These plants differ considerably in appearance; they have a different flavour and emit a different odour; they flower at slightly different periods; they grow in somewhat different stations; they ascend mountains to different heights; they have different geographical ranges; and lastly, according to very numerous experiments made during several years by