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The most remarkable case of its appearance among higher forms is that of the marine Ascidians, or tunicates close allies of the true vertebrates where reproduction by budding and the formation of wonderfully elaborate star-like forms produced by budding and the cohesion of the budded individuals as one composite individual are well known.
This fish is remarkable for its negative characters; it can hardly be said to possess a brain, vertebral column, or heart, etc.; so that it was classed by the older naturalists amongst the worms. Many years ago Prof. Goodsir perceived that the lancelet presented some affinities with the Ascidians, which are invertebrate, hermaphrodite, marine creatures permanently attached to a support.
This creature, if its whole structure had been examined by a naturalist, would have been classed among the Quadrumana, as surely as the still more ancient progenitor of the Old and New World monkeys. This animal seems to have been more like the larvæ of the existing marine Ascidians than any other known form.
Goodsir long ago insisted upon the resemblance between Amphioxus and the Ascidians; but the notion of a genetic connection between the two, and especially the identification of the notochord of the Vertebrate with the axis of the caudal appendage of the larva of the Ascidian, is a novelty which, at first, takes one's breath away.
Now, there is a class of animals called Ascidians, which possess a heart and a circulation, and up to the period of which I speak, no one would have dreamt of questioning the propriety of the deduction, that these creatures have a circulation in one direction; nor would any one have thought it worth while to verify the point.
How dare you, sir, with your imperfect faculties and your perfunctory method of research, which can only cover an infinitesimal period in the existence of this planet, venture to limit the potentialities of those laws which have already converted us from ascidians into men, and which may as easily evolve in us the faculty of hearing tom-toms in the Himalayas while we are sitting here, as of that articulate speech or intelligent reasoning which, owing to their operation, we now possess?
Now, there is a class of animals called Ascidians, which possess a heart and a circulation, and up to the period of which I speak, no one would have dreamt of questioning the propriety of the deduction, that these creatures have a circulation in one direction; nor would any one have thought it worth while to verify the point.
Conklin had found out in 1904 and 1905 that the egg cytoplasm in Ascidians is not only composed of different materials, but that these give rise to definite structures in the embryo later on. If we look at these views from one angle, the apparent conflict disappears, as Professor Conklin points out. We can still presume that all the factors of inheritance are carried in the nucleus.
Some of the most fascinating cases, on account of the beauty of the little creatures concerned, are found amongst the surface-swimming Ascidians of the sea the glass-like Salps.
Morgan, T.H. A Critique of the Theory of Evolution. N.Y., 1916, pp. 1-27. Loeb, Jacques. Artificial Parthenogenesis and Fertilization. Chicago, 1913, pp. 3, 51f., 240f, 303. Conklin, E.G. Organ-Forming Substances in the Eggs of Ascidians. U. of Pa. Contrib. from the Zool. Lab. Vol. 12. 1905, pp. 205-230. Loeb, J. The Organism as a Whole. N.Y., 1916, pp. 138f, 151-2. Guyer, M.F. Being Well-Born.
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