consideration.

The significance of the aphorisms that precede the lectures on the Natural Orders is not easy to apprehend. These are expressed with the utmost formality, and we cannot doubt that in them we have Linnaeus's own words, though for the record we are dependent on the transcripts of his pupils.

The text of the first five is as follows:

1. Creator T. O. in primordio vestiit Vegetabile Medullare principiis constitutivis diversi Corticalis unde tot difformia individua, quot Ordines Naturales prognata.

2. Classicas has (1) plantas Omnipotens miscuit inter se, unde tot Genera ordinum, quot inde plantae.

3. Genericas has (2) miscuit Natura, unde tot Species congeneres quot hodie existunt.

4. Species has miscuit Casus, unde totidem quot passim occurrunt, Varietates.

5. Suadent haec (1-4) Creatoris leges a simplicibus ad Composita.

Naturae leges generationis in hybridis.

Hominis leges ex observatis a posteriori.

I am not clear as to the parts assigned in the first sentence respectively to the "Medulla" and the "Cortex," beyond that Linnaeus conceived that multiformity was first brought about by diversity in the "Cortex." The passage is rendered still more obscure if read in connection with the essay on "Generatio Ambigena," where he expresses the conviction that the Medulla is contributed by the mother, and the Cortex by the father, both in plants and animals.[5]

But however that may be, he regards this original diversity as resulting in the constitution of the Natural Orders, each represented by one individual.

In the second aphorism the Omnipotent is represented as creating the genera by intermixing the individual plantae classicae, or prototypes of the Natural Orders.

The third statement is the most remarkable, for in it he declares that Species were formed by the act of Nature, who by inter-mixing the genera produced Species congeneres, namely species inside each genus, to the number which now exist. Lastly, Chance or Accident, intermixing the species, produced as many varieties as there are about us.

Linnaeus thus evidently regarded the intermixing of an originally limited number of types as the sufficient cause of all subsequent diversity, and it is clear that he draws an antithesis between Creator, Natura, and Casus, assigning to each a special part in the operations. The acts resulting in the formation of genera are obviously regarded as completed within the days of the Creation, but the words do not definitely show that the parts played by Nature and Chance were so limited.

Recently also E. L. Greene[6] has called attention to some curious utterances buried in the Species Plantarum, in which Linnaeus refers to intermediate and transitional species, using language that even suggests evolutionary proclivities of a modern kind, and it is not easy to interpret them otherwise.

Whatever Linnaeus himself believed to be the truth, the effect of his writings was to induce a conviction that the species of animals and plants were immutably fixed. Linnaeus had reduced the whole mass of names to order and the old fantastical transformations with the growth of knowledge had lapsed into discredit; the fixity of species was taken for granted, but not till the overt proclamation of evolutionary doctrine by Lamarck do we find the strenuous and passionate assertions of immutability characteristic of the first half of the nineteenth century.

It is not to be supposed that the champions of fixity were unacquainted with varietal differences and with the problem thus created, but in their view these difficulties were apparent merely, and by sufficiently careful observation they supposed that the critical and permanent distinctions of the true species could be discovered, and the impermanent variations detected and set aside.

This at all events was the opinion formed by the great body of naturalists at the end of the eighteenth and beginning of the nineteenth centuries, and to all intents and purposes in spite of the growth of evolutionary ideas, it remains the guiding principle of systematists to the present day. There are 'good species' and 'bad species' and the systematists of Europe and America spend most of their time in making and debating them.

In some of its aspects the problem of course confronted earlier naturalists. Parkinson for instance (1640) in introducing his treatment of Hieracium wrote, "To set forth the whole family of the Hawkeweedes in due forme and order is such a world of worke that I am in much doubt of mine own abilitie, it having lyen heavie on his shoudiers that hath already waded through them ... for such a multitude of varieties in forme pertaining to one herbe is not to be found againe in rerum natura as I thinke," and the same idea, that the difficulty lay rather in man's imperfect powers of discrimination than in the nature of the materials to be discriminated, is reflected in many treatises early and late.

It was however with the great ouburst of scientific activity which followed Linnaeus that the difficulty became acute. Simultaneously vast masses of new material were being collected from all parts of the world into the museums, and the products of the older countries were re-examined with a fresh zeal and on a scale of quantity previously unattempted. But the problem how to name the forms and where to draw lines, how much should be included under one name and where a new name was required, all this was felt, rather as a cataloguer's difficulty than as a physiological problem. And so we still hear on the one hand of the confusion caused by excessive "splitting" and subdivisions, and on the other of the uncritical "lumpers" who associate together under one name forms which another collector or observer would like to see distinguished.

In spite of Darwin's hopes, the acceptance of his views has led to no real improvement—scarcely indeed to any change at all in either the practice or aims of systematists. In a famous passage in the Origin he confidently declares that when his interpretation is generally adopted "Systematists will be able to pursue their labours as at present; but they will not be incessantly haunted by the shadowy doubt whether this or that form be a true species. This, I feel sure, and I speak after experience, will be no slight relief. The endless disputes whether or not some fifty species of British brambles are good species will cease." Those disputes nevertheless proceed almost exactly as before. It is true that biologists in general do not, as formerly, participate in these discussions because they have abandoned systematics altogether; but those who are engaged in the actual work of naming and cataloguing animals and plants usually debate the old questions in the old way. There is still the same divergence of opinion and of practice, some inclining to make much of small differences, others to neglect them.

Not only does the work of the systematists as a whole proceed as if Darwin had