The aquiferous tubes specified above open into this canal. But the same thing may be found under various modifications in other genera of the family. Since I have succeeded in injecting colored liquid into the beroids, for instance, and keeping them alive with it circulating in their transparent mass, I am able to show the identity of their zones of locomotive fringes (combs), from which they take their name of Ctenophorae, with the ambulacral (locomotive) apparatus of the echinoderms. Furnished with these facts, it is not difficult to recognize true beroidal forms in the embryos of sea-urchins and star-fishes, published by Muller in his beautiful plates, and thus to trace the medusoid origin of the echinoderms, as the polypoid origin of the medusae has already been recognized. I do not here allude to their primitive origin, but simply to the general fact that among radiates the embryos of the higher classes represent, in miniature, types of the lower classes, as, for instance, those of the echinoderms resemble the medusae, those of the medusae the polyps. Having passed the greater part of last winter in Florida, where I was especially occupied in studying the coral reefs, I had the best opportunity in the world for prosecuting my embryological researches upon the stony corals. I detected relations among them which now enable me to determine the classification of these animals according to their mode of development with greater completeness than ever before, and even to assign a superior or inferior rank to their different types, agreeing with their geological succession, as I have already done for the fishes. I am on the road to the same results for the mollusks and the articulates, and can even now say in general terms, that the most ancient representatives of all the families belonging to these great groups, strikingly recall the first phases in the embryonic development of their successors in more recent formations, and even that the embryos of comparatively recent families recall families belonging to ancient epochs. You will find some allusion to these results in my Lectures on Embryology, given in my "Lake Superior," of which I have twice sent you a copy, that it might reach you the more surely; but these first impressions have assumed greater coherence now, and I constantly find myself recurring to my fossils for light upon the embryonic forms I am studying and vice versa, consulting my embryological drawings in order to decipher the fossils with greater certainty.