The Principles of Biology, Volume 1 · Herbert Spencer
NOTES
Doubtless the Rev. Professor was prompted to make this assertion by the desire to discredit the work he was attacking; and having so good an end in view, thought it needless to be particular about the means. In the art of dealing with the language of opponents, Dr. Watts might give lessons to Monsignor Capel and Archbishop Manning. _December 28th, 1874._ [2] In this passage as originally written (in 1862) they were described as incondensible; since, though reduced to the density of liquids, they had not been liquefied. [3] Here and hereafter the word "atom" signifies a unit of something classed as an element, because thus far undecomposed by us. The word must not be supposed to mean that which its derivation implies. In all probability it is not a simple unit but a compound one. [4] The name hydro-carbons was here used when these pages were written, thirty-four years ago. It was the name then current. In this case, as in multitudinous other cases, the substitution of newer words and phrases for older ones, is somewhat misleading. Putting the thoughts of 1862 in the language of 1897 gives an illusive impression of recency. [5] It will perhaps seem strange to class oxygen as a crystalloid. But inasmuch as the crystalloids are distinguished from the colloids by their atomic simplicity, and inasmuch as sundry gases are reducible to a crystalline state, we are justified in so classing it.
As, along with the idea just named, the dropped portion of the original essay contains other ideas which seem to me worth preserving, I have thought it as well to reproduce it, in company with the chief part of the general argument as at first sketched out. It will be found in Appendix A to this volume. [28] Unfortunately the word _heterogenesis_ has been already used as a synonym for "spontaneous generation." Save by those few who believe in "spontaneous generation," however, little objection will be felt to using the word in a sense that seems much more appropriate. The meaning above given to it covers both Metagenesis and Parthenogenesis. [29] Prof. Huxley avoids this difficulty by making every kind of Genesis a mode of development. His classification, which suggested the one given above, is as follows:-- { Growth { Continuous { { { Metamorphosis { Development { { { Metagenesis { { Agamogenesis { { Discontinuous { { Parthenogenesis { Gamogenesis [30] The implication is that an essentially similar process occurs in those fragments of leaves used for artificial propagation. Besides the Begonias in general, I learn that various other plants are thus multiplied--Citron and orange trees, _Hoya carnosa_, _Aucuba japonica_, _Clianthus puniceus_, etc., etc. _Bryophyllum calicinum_, _Rochea falcata_, and _Echeveria_. I also learn that the following plants, among others, produce buds from their foliage leaves:--_Cardamine pratensis_, _Nasturtium officinale_, _Roripa palustris_, _Brassica oleracea_, _Arabis pumila_, _Chelidonium majus_, _Nymphæa guianensis_, _Episcia bicolor_, _Chirita sivensis_, _Pinguicula Backeri_, _Allium_, _Gagea_, _Tolmia_, _Fritillaria_, _Ornithogalum_, etc. In _Cardamine_ and several others, a complete miniature plant is at once produced; in other cases bulbils or similar detachable buds.
While this chapter is under revision, another noteworthy illustration has been furnished to me by a wall-trained pear tree which was covered in the spring by luxuriant "foreright" shoots. As I learned from the gardener, it was pruned just as the fruit was setting. A large excess of sap was thus thrown into other branches, with the result that in a number of them the young pears were made monstrous by reversion. In some cases, instead of the dried up sepals at the top of the pear, there were produced good sized leaves; and in other cases the seed-bearing core of the pear was transformed into a growth which protruded through the top of the pear in the shape of a new shoot.
Superfluous size of an organ implies several evils:--Its original cost is greater than requisite, and other organs suffer; the continuous cost of its nutrition is unduly great, involving further injury; it adds needlessly to the weight carried and so again is detrimental; and there is in some cases yet a further mischief--it is in the way. Clearly, then, those in which _plus_ variations of the organ have occurred are likely to be killed off as well as those in which _minus_ variations have occurred; and hence there is no proof that the survival-mean will exceed the birth-mean. Moreover the assumption has a fatal implication. To say that the survival-mean of an organ is greater than the birth-mean is to say that the organ is greater _in proportion to other organs_ than it was at birth. What happens if instead of one organ we consider all the organs? If the survival-mean of a particular organ is greater than its birth-mean, the survival mean of each other organ must also be greater. Thus the proposition is that every organ has become larger in relation to every other organ!--a marvellous proposition. I need only add that Dr. Romanes' inferences with respect to the two other causes--atavism and failing heredity--are similarly vitiated by ignoring the plus variations and their effects. [58] _Westminster Review_, January, 1860. See also _Essays, &c._, vol. i, p. 290.
To me it seems manifest that "increased interest and attention" will not enable a patient to discriminate two points where a few minutes before he could perceive only one. That which he can really do in this short time is to learn to discriminate between the _massiveness of a sensation_ produced by two points and the massiveness of that produced by one, and to _infer_ one point or two points accordingly. Respecting the existence of sensation-areas marked off from one another, I may, in the first place, remark that since the eye originates as a dermal sac, and since its retina is a highly developed part of the sensitive surface at large, and since the discriminative power of the retina depends on the division of it into numerous rods and cones, each of which gives a separate sensation-area, it would be strange were the discriminative power of the skin at large achieved by mechanism fundamentally different. In the second place I may remark that if Mr. Cattell will refer to Professor Gustav Retzius's _Biologische Untersuchungen_, New Series, vol. iv (Stockholm, 1892), he will see elaborate diagrams of superficial nerve-endings in various animals showing many degrees of separateness. I guarded myself against being supposed to think that the sensation-areas are sharply marked off from one another; and suggested, contrariwise, that probably the branching nerve-terminations intruded among the branches of adjacent nerve-terminations. Here let me add that the intrusion may vary greatly in extent; and that where the intruding fibres run far among those of adjacent areas, the discriminativeness will be but small, while it will be great in proportion as each set of branching fibres is restricted more nearly to its own area. All the facts are explicable on this supposition.
Text from Project Gutenberg, public domain in the United States.