Notes on Medusa: of the Western Atlantic. 151 



of the larval forms, their multiplication and metamorphosis, but he lacked 

 material for a study of the development of the sexual organs in the adult, 

 and the early larval phases. Indeed, strangely enough, there seems to be 

 no certainty as to the sexual character of the creatures whether they are 

 hermaphrodite or have separate sexes. The latter condition is assumed to 

 obtain by some writers on the genus. 



In the hope of determining some of the main points in the sexual mul- 

 tiplication of Cassiopea, large numbers of medusae were taken from the 

 moat and transferred to aquaria and live-cars at the Carnegie Institution 

 Laboratory on Loggerhead Key. As Dr. Mayer has beautifully demon- 

 strated, 1 no more favorable material can be imagined for all sorts of labo- 

 ratory observations and experimentation than this same Cassiopea. It lives 

 remarkably well in small aquaria. 



Parasitic (f) larva. When the medusae are left for only a short time 

 in a jar, and then removed, the water is found to contain floating masses 

 or clouds of mucus. Microscopic examination of this mucus shows multi- 

 tudes of nematocysts, discharged or intact, singly or in small clusters, float- 

 ing in it. Also included in this substance, or suspended in the water outside 

 of it, there appeared great numbers of very small organisms -which I, and 

 others, took for embryos of the medusa. These small objects appeared in 

 several shapes, suggesting successive stages in growth and metamorphosis, 

 and it looked as if it should be an easy task to get the full series of phases 

 in the development of the Cassiopea egg. After some days of careful watch- 

 ing it was necessary to conclude, in disappointment, that these creatures 

 were the parasitic young of some other animal ; that they were probably not 

 even of coelenterate origin. 



These organisms were bilaterally symmetrical, not radial, having three 

 lobes separated by clear-cut incisions at one end, the larger, and two at the 

 other. They were clear, almost entirely transparent, and colorless in the 

 earliest stages. With increasing size the number of lobes accessory to the 

 first set increases, much as in the echinoderm larva, and there appear in 

 the interior of the creature unicellular zoanthellae, which give a yellow and 

 later a brown cast to the organism. 



The surface was granular in appearance, a condition which was due to 

 the presence of innumerable minute spherical bodies, arranged in regular 

 pattern, suggesting in a general way the follicle cells of ascidians. Around 

 the margins of the rounded lobular projections, cilia in bands served to 

 drive the larva through the water in a rotating motion. Comparison of 

 these objects with the ovarian eggs of the medusa, together with a consid- 

 eration of the surface appearance and the peculiar contour of the body, made 

 it impossible to regard this organism as of ccelenterate affinities. Further 



'Mayer, A. G. 1906. Carnegie Institution Publication, No. 47, Rhythmical Pulsa- 

 tion in Scyphomedusse. 



