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organism in just those cases which, from the special creation stand-point, can appear only as bunglingly complex contrivances to secure a simple result, who can doubt which view of the matter is the true one ?
THE TESTIMONY OF EMBRYOLOGY.
THE present chapter will try to explain the
bearing of the development of individual animals or plants, from the moment when life begins, on the general theory of organic evolution.
But it will first be necessary for the reader who is not already somewhat familiar with the outlines of classification of animals and plants, to consult a brief account 1 of the leading types or forms of life met with in the animal and in the vegetable kingdom ; since, without this elementary knowledge, the facts of this and the following chapter cannot be appreciated, nor their bearing on the development theory understood.
At the bottom of the lowest sub-kingdom of animals, the protozoa, is the class monera, ac
1 See Appendix A.
cording to Haeckel. Seen through the microscope, one of these simplest of animals appears at first as a mere roundish or irregular-shaped speck of animated jelly (protoplasm) of about the same size 1 one of the colorless cells (white blood-corpuscles) which are found in human blood, that is, about the three thousandth of an inch in diameter. Soon, it may be, this speck will be seen to put forth from any part of itself little blunt extensions, false-feet, we call them, and to creep about very slowly by reaching forward with some of these false-feet, then drawing itself forward to where their extremities were placed, and so on. A particle of some vegetable substance comes into contact with one of these feet; and at once the living jelly flows out, around, and over the foreign material, till the latter is quite enclosed, and here it stays till whatever was nourishing has been absorbed from it, when the indigestible portion is squeezed out through any part of the body of the animal, and so rejected. The protamæba (for this is the animal's name) has no eyes, ears, nose, mouth, lungs, heart, stomach, nor any digestive organs, so far as the best microscope can see; its chemical composition is much the same as that of the white of an egg ; and it differs from an extremely small drop of this substance mainly in being alive. That it is alive is evident, not only from the fact of its moving and feeding in the way already described, but also from the fact of its reproducing. One of the largest among a number of these minute organisins may often be noticed to become drawn in or smaller about the mid
1 The dimensions, however, are very variable. 2 Pseudopodia.
dle: it assumes a sort of hour-glass shape, and soon separates into two parts, thus producing two animals from one by self-division as it is called.
Ascending a step above the monera, we find animals of the genus amoeba, with a little more variety of parts than the Protamoba possessed, since each contains within its jelly-like mass a particle of firmer consistency than the rest, called the nucleus; and this nucleus often shows within itself the presence of a still smaller particle, the nucleolus. Somewhere within the body of the amaba there is also a little sac, which alternately grows larger, and almost disappears, expanding and contracting like a microscopic heart. When the amoeba is reproduced (as it always is) by self-division, the only essential difference between the process and that already described in the case of the Protamæba is, that the operation now begins by the pinching-in of the kernel or nucleus, followed by a division of the whole animal as before. In some species, too, it may be noticed that the whole bit of protoplasmic jelly which composes the animal becomes covered with a tougher coating, and the body becomes more nearly spherical in shape, before the process of self-division begins. In one orange-colored moner described by Professor Haeckel," the life-history is in many ways remarkable.