Page:Popular Science Monthly Volume 10.djvu/235

 tracks, some of which are marvelously like bird’s tracks, we should not come upon exactly that series of transitions by which in former days the reptile was connected with the bird.

I don’t think, ladies and gentlemen, that I need insist upon the value of evidence of this kind. You will observe that, although it does not prove that birds have originated from reptiles by the gradual modification of the ordinary reptile into a dinosaurian form, and so into a bird, yet it does show that such a process may possibly have taken place, and it does show that, in former times, there existed creatures which filled up one of the largest gaps in existing animate nature, and that was exactly the kind of evidence which I stated to you in starting we are bound to meet with in rocks if the hypothesis of evolution be correct.

In my third and last lecture I will take up what I venture to call the demonstrative evidence of evolution.



HERE are a large number of different kinds of moths, inhabiting North America and Europe, which entomologists have classified under the technical family term, Noctuæ. Of this family, 1,028 different species have been catalogued as European. There being very many students, and a sufficient time having elapsed to secure a thorough collecting throughout the territory, this number may be taken as sufficiently corresponding with the actual representation of the family in Europe. In North America nearly 1,200 species are now catalogued, but, since much of our territory remains to be explored in this respect, we may expect considerable additions to the number of known Noctuæ inhabiting our continent. The greater number of the species may be easily distinguished on comparison, the American from the European. There are, however, certain American species which differ but very slightly from certain European, and hence are generally called “representative species,” or “species of replacement.” For instance, Apatela occidentalis (G. and R.) “represents” the European Apatela psi (Linn.); Agrotis Normaniana (Grote), the European Agrotis triangulum; Calocampa nupera (Lintner), the European Calocampa vetusta; Catocala relicta (Walk.), the European Catocala fraxini, etc.

Although the number of such species appears relatively small, 