PAET II: GENERAL DESCRIPTION OF THE ANATOMY OF THE 



CUBOMEDUS^. 



A: CHARYBDEA XAYMACANA. 

 a. Environment and habit of life. 



1. The Cubomedusse 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. Xaymacana was taken regularly a few yards 

 off-shore from a strip of sandy beach not ten minutes row from the 

 laboratory at Port Henderson. It was seen only in the morning before 

 the sea-breeze came in to roughen the water and to turn the region of its 

 placid feeding-ground into a dangerous lee-shore. Some of the speci- 

 mens taken contained in the stomach small fish so disproportionately 

 large in comparison with the stomach that they lay coiled up, head over- 

 lapping tail. The name Charybdea, then, from the Greek %apvfi<>ig (a gulf, 

 rapacious), seems to be no misnomer. It is worth mentioning that the 

 digestive juices left the nervous system of the fish intact, so that from 

 the stomach of a Charybdea could be obtained beautiful dissections, or 

 rather macerations, of the brain, cord, and lateral nerves of a small fish. 



In size C. Xaymacana agrees very well with the average of the 

 genus. The four single tentacles characteristic of the genus are very 

 contractile, varying from two or three to six or seven inches in length, 

 and probably if measurements could be taken while the animal was 

 swimming freely about, the length would be found to be greater still. 

 Charybdea is a strong and active swimmer, and presents a very beau- 

 tiful appearance in its movements through the water, the quick, vigorous 

 pulsations contrasting sharply with the sluggish contractions seen in 

 most Scyphomedusae. With its tentacles streaming gracefully behind, 

 an actively swimming Charybdea presents a fanciful resemblance to a 



