152 Papers from the Marine Biological Laboratory at Tortngas. 



than that I was unable to go, and am still quite in the dark as to the nature 

 of these curious bits of animal life. 



Mucus masses. The presence of these larval creatures in the mucus 

 clouds excreted by Cassiopea gave rise to the notion that the reproductive 

 organs must secrete this mucus, which was useful as a vehicle for the sperm- 

 cells. It was afterwards seen, however, that the clouds of mucus originated 

 not in the genital pouches but from the oral arms. They probably serve to 

 entrap and hold minute animalcules and other prey for food, having the 

 same origin and function as the similar product in corals. 1 These sluggish 

 rhizostomes come nearer to the actinians in point of habit than do most of 

 the ccelenterates, and it would not be surprising to find that both their food 

 and their mode of capturing it were somewhat similar. 



Failing in my attempt to get the larval stages by natural means, I tried 

 artificial fertilization of the eggs, or rather I took the preliminary steps 

 thereto. But I was unable to discover any sperm ! All the medusae that 

 I examined proved to be females, and no organs but the ovaries appeared 

 within the genital pouches. Over one hundred of the medusae were opened 

 in the laboratory, with the result that every individual was found to have 

 ovarian eggs in the vermiform gonads, in all stages of maturation. 



It was disappointing to fail of getting the larvae of this interesting 

 medusa, and that, too, without having any explanation to fall back upon. 

 True, it did not seem to be the normal breeding-season, prolonged search 

 having brought to light only a few larvae in the scyphistoma stage, and only 

 a single free ephyrula. But these few young stages indicated that there 

 was some activity in the reproductive functions of the members of the 

 species there in the moat. At the height of the breeding-season there would 

 undoubtedly be no difficulty in finding many immature stages. Bigelow 

 reports that at the time of his observations in Jamaica the stones and sticks 

 in Salt Pond were thick with the scyphistomas. It certainly looks as if the 

 creature were hermaphrodite, and the indications are that it is also proto- 

 gynous. 



Polyclonia frondosa Agassiz. 



While collecting in the moat one morning early in July, 1905, my eye 

 caught the sparkle of clear white spots upon the oral arms of a medusa on 

 the sandy bottom. When it was brought to the surface, these white spots 

 were found to be small scales about the size and shape of an apple seed, 

 except that they were flatter, attached to the surface of the arm by the small 

 pointed end. The fleshy yellow tentacle-like appendages, which are so 

 characteristic in Cassiopea were entirely absent, and the scales seemed to 

 take their place. The general color-tone of the medusa was noticeably dif- 

 ferent from that which prevails in Cassiopea. There was a more trans- 

 parent appearance, with the brownish yellow turned to olive-brown, and the 



1 Duerden, J. E., 1904. The Coral Siderastrea radians and its Postlarval Develop- 

 ment. Carnegie Institution of Washington. Publication 20, page 6, footnote. 



