Page:Popular Science Monthly Volume 71.djvu/218

212 of which the actual embryo is gradually formed. In No. 1 merely the axis is indicated, in front of and alongside of which the parts of the embryo are to arise, as is suggested by Nos. 2, 3, 4, 5, These stages cover the seventh and eighth days. Nos. 6 to 14 figure actual embryos, No. 6 of nine and a half, No. 14 of fifteen days. No. 6 is singularly twisted into a spiral form, the reason for which is still undiscovered. No. 9 shows the condition at eleven days—notice the limbs, a leg in front and a leg behind, each only a small mound as yet upon the surface

of the body; the distinct eye, the protuberance caused by the heart. Nos. 11 and 12 show the embryonic shape at twelve and a half and at thirteen days—there has been a great increase of size with accompanying modifications of form. The next pair, Nos. 13 and 14, present us embryos of fourteen and fifteen days, respectively, and you see that the growth is very marked indeed, and the change of form obvious; the creature is now changing from the embryonic type into something resembling a rabbit. Other pictures could readily be added, but, though two weeks must still elapse before the animal will be ready to enter the world, it is not necessary for my present purpose to include this period in our survey. We need only contemplate, it seems to me, the series of drawings in Fig. 37 to realize that the early embryonic growth