Origin of Species Variorum

from some one prototype. But analogy may be a deceitful guide. Nevertheless all living things have much in common,— in their chemical composition, their ... cellular structure, .. their laws of growth, and their liability to injurious influences. We see this even in so trifling a circumstance as that the same poison often similarly affects plants and animals; or that the poison secreted by the gall-fly produces monstrous growths on the wild rose or oak-tree. In all organic beings the union of a male and female elemental cell seems occasionally to be necessary for the production of a new being. ↑ In all, as far as is at present known, the germinal vesicle is the same. So that every individual organic being starts from a common origin. If we look even to the two main divisions— namely, to the animal and vegetable kingdoms— certain low forms are so far intermediate in character that naturalists have disputed to which kingdom they should be referred, and, as Professor Asa Gray has remarked, "the spores and other reproductive bodies of many of the lower algæ may claim to have first a characteristically animal, and then an unequivocally vegetable existence." Therefore, on the principle of natural selection with divergence of character, it does not seem incredible that, from some such low and intermediate form, both animals and plants may have been developed; and, if we admit this, we must admit that all the organic beings which have ever lived on this earth may have descended from some one primordial form. .. .. .. .. .. ... But this inference is chiefly grounded on analogy, and it is immaterial whether or not it be accepted. The case is different with the members of each great class, as the Vertebrata, the Articulata, &c.; for here, as I have just remarked, we have in the laws of homology and embryology, &c.; distinct evidence that all have descended from a single parent.