A DISSERTATION PRESENTED FOR THE DEGREE OF DOCTOR OF PHILOSOPHY, IN THE JOHNS HOPKINS UNIVERSITY, 1897 BY FRANKLIN STORY CONANT A MEMORIAL VOLUME BALTIMORE The Johns Hopkins Press 1898 PRINTED BY The Lord Baltimore Press THE FRIEDENWALD COMPANY BALTIMORE, MD., U. S. A. With the kind regards of Franklin Story Conant. THE HELIOTYPE PRINTING CO. BOSTON...

This Treatise is printed after the author’s death, as a Memorial by his friends, fellow-students and instructors, with the aid of the Johns Hopkins University. It consists of his Dissertation, reprinted from the copy which was accepted by this University at his examination for the degree of Doctor of Philosophy in June, 1897. As he had made many notes on the embryology of the Cubomedusæ, and had hoped to complete and publish them together with an account of physiological experiments with these m

1. Description of Two New Chaetognaths. Johns Hopkins University Circulars, No. 119, June, 1895. 2. Notes on the Chaetognaths. Johns Hopkins University Circulars, No. 126, June, 1896. 3. The Inhibitory and Accelerator Nerves to the Crab’s Heart ( an abstract ), by F. S. Conant and H. L. Clark. Johns Hopkins University Circulars, No. 126, June, 1896. 4. On the Accelerator and Inhibitory Nerves to the Crab’s Heart , by F. S. Conant and H. L. Clark. The Journal of Experimental Medicine, Vol. I, No.

Jelly-fish offer to the lover of natural history an inexhaustible store of beauty and attractiveness. One who has studied them finds within him a ready echo to Haeckel’s statement that when first he visited the seacoast and was introduced to the enchanted world of marine life, none of the forms that he then saw alive for the first time exercised so powerful an attraction upon him as the Medusæ. The writer counts it a rare stroke of fortune that he was led to the study of a portion of the group b

Characteristics: Acraspeda with four perradial sensory clubs which contain an auditory club with endodermal otolith sac and one or several eyes. Four interradial tentacles or groups of tentacles. Stomach with four wide perradial rectangular pockets, which are separated by four long and narrow interradial septa, or cathammal plates. Gonads in four pairs, leaf-shaped, attached along one edge to the four interradial septa. They belong to the subumbrella, and are developed from the endoderm of the s

1. The Cubomedusæ are generally believed to be inhabitants of deep water which come to the surface only occasionally. Both of the Jamaica species, however, were found at the surface of shallow water near the shore, and only under these circumstances. Whether these were their natural conditions, or whether the two forms were driven by some chance from the deep ocean into the Harbor and there found their surroundings secondarily congenial, so to speak, can be a matter of conjecture only. C. Xaymac

The species upon which the new family was founded was obtained in great abundance in one locality in Kingston Harbor in the summer of 1896. The environment was even more unlike that in which Cubomedusæ have been found heretofore than in the case of Charybdea Xaymacana. On the west side of the Harbor there is a part more or less cut off from the main body of water, and so from the ocean, by a peninsula. This sheltered bay is dotted with small mangrove islands which toward the head of the bay beco

In Medusæ it is a common thing to find that in certain definite places of the gastro-vascular system two endodermal surfaces that were primarily separated by a space have come together and fused into a single lamella or plate. Such a structure is called indifferently a cathammal plate, an endodermal lamella, or a vascular lamella. In the adult animal the vascular lamellæ are by virtue of their very nature formations “with a past.” They are scaffolding left in the completed structure, giving us c

The nervous system of the Cubomedusæ is the most highly developed that is found in any of the jelly-fishes. If the position of the group among the Acraspeda is established, it alone is ample to prove that the Hertwigs had not sufficient evidence when they stated in their monograph on the nervous system of the Medusæ (’78) that the Acraspeda show a much lower nervous organization than the Craspedota. The system naturally groups itself under three heads, the nerve ring, the sensory clubs, and the

Clarke, H. J. ’78. Lucernariæ and their Allies. Washington: Smithsonian Institution. Claus, C. ’78. Ueber Charybdea marsupialis. Arb. aus d. Zool. Inst. d. Univ. Wien, Band II, Heft 2. Doflein, F. ’96. Die Eibildung bei Tubularia. Zeitsch. f. wiss. Zool., Bd. LXII, Heft 1. Haeckel, E. ’79. Das System der Medusen. Jena.—’81. Challenger Report on the Deep-sea Medusæ. Vol. IV. Hertwig, O. and R. ’78. Das Nervensystem und die Sinnesorgane der Medusen. Leipzig. Hesse, R. ’95. Ueber das Nervensystem u

Fig. 1. Charybdea Xaymacana, from one of the four interradial sides. Fig. 2. The same from above. Fig. 3. The same from below, the four tentacles cut off. Fig. 4. The same cut in halves vertically (or radially) through a perradius. Fig. 5. The same out in halves vertically (or radially) through an interradius. Figs. 6-16. Diagrams of horizontal (or transverse) sections through C. Xaymacana at successive levels. Fig. 17. Tripedalia cystophora, from one of the four interradial sides. Fig. 18. The