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The past season has seen the production of Mr. Darwin's new work on the 'Fertilisation of Orchids,' in which he has set forth, with much skill and interesting detail, the various and often highly complicated contrivances by which, among this extensive group of hermaphrodite plants, self-fertilisation, save in a very few exceptional instances, is rendered absolutely impossible. For the ovary of one Orchid is fertilised by the male element of another, and to affect the junction of these the intervention of insect agency is necessary. The case of the Infusoria is, in some respects, comparable, even though with them such foreign intervention be wanting. Like Orchids, they are hermaphrodite, but not self-fertilising, their fecundation being effected by constantly dissimilar elements produced in different individuals. And in both cases, this contact cannot take place without the previous occurrence of a process more or less complex, the details of which are curiously varied in their several tribes. Theoretically, nothing seems easier than for an Infusorium (or Orchid) to fertilise itself. There are indeed some Infosoria in which, so far as we at present know, the act of sexual union appears impossible. May it not be that these are capable of self-fecundation, just as in  this very respect, a few Orchids differ from the great majority of their order. Here, as  elsewhere, the exception proves the rule; and such exceptions, while they forbid the systematist to dogmatise, and warn him never to neglect the final prove of verification, are full of meaning for the philosophic student of biology. By these nature, so to speak, points out to us the simpler method, while in practice she adopts another, attended with much delay and apparent difficulty. But not without a purpose. And, perhaps, in this particular case the lesson which she seeks to convey is that which had been well expressed for us by Mr. Darwin:

"It is an astonishing fact (among Infusoria as well as in Orchid] that self-fertilisation should not have been an habitual occurrence. It apparently demonstrates to us that there must be something injurious in the process. Nature thus tells us in the most emphatic manner, that she abhors perpetual self-fertilisation

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[…] that some unknown great good is derived from the union of individuals which have been kept distinct for many generations." - J. R. G.