. The doctrine of descent and Darwinism. Evolution. 204 THE DOCTRINE OF DESCENT. the Hydractinea seems superior, inasmuch as it is itself a sexual form. The zone of spherical protuberances in the middle of the body are the ovaries or egg capsules corresponding to the sperm capsules of the male indi- vidual. HeterQgenesis does not take place in our Hy- dractinia, but, as in the development of the ovum of the Cladonema into the Stauridium, there is a transformation of a ciliated lava into a sessile polype. But it is obvious that the part which in the Hydractinia is played, by the male and female
. The doctrine of descent and Darwinism. Evolution. 204 THE DOCTRINE OF DESCENT. the Hydractinea seems superior, inasmuch as it is itself a sexual form. The zone of spherical protuberances in the middle of the body are the ovaries or egg capsules corresponding to the sperm capsules of the male indi- vidual. HeterQgenesis does not take place in our Hy- dractinia, but, as in the development of the ovum of the Cladonema into the Stauridium, there is a transformation of a ciliated lava into a sessile polype. But it is obvious that the part which in the Hydractinia is played, by the male and female sexual organs is per- formed in the generative cycle of the Cladonema by the sexual animals. By following the transition from the de- pendent organ into the independent animal, we find the solution and ex- planation of the process termed he- terogenesis. Between the genera reproduced like the Hydractinia, and those reproduced like the Cladonema, there are many others, of which the propagation shows the gradual transition of the rudimentary sexual organs into the sexual animal. We may so arrange the genera of the " Medusa polypes " as to exhibit how the parts which in the Hydractinia are mere capsules, generating and enclosing the ova, become more and more perfect. They acquire a special branch of the alimentary canal and blood-vessels, and are provided with the marginal papillae characteristic of the Medusae, and constituting their peculiar sensory organs. In short, what in one member of the systematic series may be termed an or- gan, is, in the next, the Medusa separating itself and. FIG. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Schmidt, Dr. (Eduard Oskar), 1823-1886. New York, Appleton
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