6. THE ANATOMY AND DEVELOPMENT OF CASSIOPEA XAMACHANA. 1 

 BY ROBERT PAYNE BIGELOW. 



INTRODUCTION. 



During the summer of 1891 the Marine Laboratory of the Johns Hopkins University 

 was stationed in the Island of Jamaica. It was at Port Henderson, a little hamlet 

 situated at the west side of the mouth of Kingston Harbor, at the point where the Salt 

 Pond Hill, eight hundred feet high, descends to the salinas and mangrove swamp* 

 surrounding the mouth of the Rio Cobre. On the other side of the hill, and to the south 

 of it, there is a considerable body of salt water, known as the Great Salt Pond. It is 

 completely separated from the sea, but only by a beach of sand, which at its narrowest 

 part is not more than a few rods in width ; and it is said by those who live near that in 

 times of storm or freshet this barrier may be broken through. 



One morning in June Dr. G. W. Field was hunting birds along the seaward shore of 

 this pond, and came upon a little bay that forms a deep indentation in the barrier and is 

 connected with the pond by a narrow inlet. The bay is overhung by low cashaw and 

 mangrove trees. At one side is a sunny sandy spot where a crocodile had made its bed, 

 and a fresh zigzag mark showed where it had recently slid into the water. A school of 

 fish was circling about in the clear water, and barnacles and sea-anemones spread their 

 tentacles from the submerged roots of the mangroves, while the bottom at the inner end 

 of the bay was completely carpeted by a colony of beautiful rhizostomatous medusae. 



A few very small specimens might be seen swimming about, but most of the medusae, 

 especially the larger ones, would not ordinarily leave the bottom. They lay there upon 

 their backs, with their voluminous, branching mouth parts spread out over their discs, 

 which were motionless, except for occasional flaps of their margins. If any of these 

 animals were disturbed, they would, however, swim about like ordinary medusae ; but 

 before long they would settle down again and assume their usual attitude upon the bottom. 



1 An earlier draft of this paper was accepted in May, 1802, by the Board of University Studies in the Johns Hopkins 

 University as a thesis for the Degree of Doctor of Philosophy. During the years 1891-92 and 1892-93 I held the Adam T. 

 Bruce Fellowship in the Johns Hopkins University, and WHS thus enabled to make a second journey to Jamaica. Publication 

 has been delayed in order that the results of this journey might be incorporated in the paper, and it is hoped that the greater 

 accuracy and completeness thus obtained have added materially to its value. 



