statement, biologists "trace back the dog's and the man's development, and they find that at a certain stage of their existence, the two creatures are not distinguishable the one from the other." What is the inference to be drawn? If the two are not distinguishable, our powers of distinguishing are insufficient, for no biologist suggests that the two are alike. The difficulty of distinguishing two germs, or two examples of fœtus, is analogous to the difficulty which Darwin has pointed out of distinguishing the orders of dogs when they are six-days-old puppies, or the breed of three-days-old colt, or of nestling pigeons. At these stages, the animals may be so similar, that it is hardly possible to distinguish them, and yet in the full grown state they are quite different (Darwin's _Origin of Species_, sixth edition, p. 391). Mr. Darwin has presented the outstanding facts thus;--"The very general, though not universal, difference in structure between the embryo and the adult;--the various parts in the same individual embryo, which ultimately become very unlike and serve for diverse purposes, being at an early period of growth alike;--the common, but not invariable resemblance between the embryos or larvæ of the most distinct species in the same class;--the embryo often retaining whilst within the egg or womb, structures which are of no service to it, either at that or at a later period of life." VI. NON-ADVANCEMENT OF LOWER ORDERS. _Page_ 158. Mr. Darwin's answer to the difficulty put by Agassiz is this;--"On our theory the continued existence of lowly organisms offers no difficulty; for natural selection, or the survival of the fittest, does not necessarily include progressive development,--it only takes advantage of such variations as arise and are beneficial to each creature under its complex relations of life."--_Origin of Species_, sixth edition, p. 98. This wears the aspect of a limitation of the theory, and to that extent an acknowledgment of the force of the reasoning of Agassiz. VII. PROTOPLASM. _Page_ 131. "Protoplasm, simple or nucleated, is the formal basis of all life;" thus "all living forms are fundamentally of one character." "All the forms of Protoplasm which have yet been examined contain the four elements, carbon, hydrogen, oxygen, and nitrogen, in very complex union." Thus there is "a general uniformity in the character of the Protoplasm, or physical basis of life, in whatever group of living beings it may be studied."--HUXLEY'S _Lay Sermons_, p. 142. VIII. NUMBER OF SPECIES OF INSECTS. _Page_ 193. Professor Huxley mentions that "Gerstsæcker in the new edition of Broun's 'Thier-Reich' gives 200,000 as the total number of species of _Arthropoda_." In this connection Mr. McLauchlan, when claiming that there are 200,000 species of Insects, adds, "In one order alone (_Coleoptera_) it is estimated that 80,000 species have been described."--_Nature_, xv. p. 275. IX. FERTILIZATION OF FLOWERS BY INSECTS. _Page_ 170.