CASSIOPEA XAMACHANA. 193 



Full-grown medusae could be kept in good condition in aquaria for a number of days, 

 and could be kept alive for weeks; while the young medusae and scyphistomas would 

 thrive there an indefinite time, if there were a little pond ooze at the bottom of the 

 aquarium and the water were changed twice a day. Indeed the growth and multiplication 

 of the scyphistomas would proceed actively under these conditions. By keeping the larvae 

 in shallow dishes I was able to watch the whole course of non-sexual development ; but the 

 development from eggs remains unknown to me because of the impossibility of finding any 

 that would develop. It was not until a few days before we left Jamaica in 1891 that I 

 discovered the habit that the very young free-swimming larvae have of hiding beneath the 

 bits of bark and the like to which the scyphistomas in the aquarium were attached, and 

 therefore the greater part of my work on the early stages of development was done during 

 the second expedition. 



After a few words concerning technique I shall begin with a systematic description of 

 the species, followed by an account of the anatomy of the adult, and the remaining part 

 of the paper will contain what I have learned of the development from the observation of 

 the living animals while in Jamaica, and by the study of sections of preserved material, 

 carried on chiefly at the Biological Laboratory of the Johns Hopkins University, but in 

 part also at the Marine Biological Laboratory of Woods Hole and at the Biological 

 Laboratory of the U. S. Fish Commission in the same place. 



I wish to express my thanks to Professor W. K. Brooks for the advice and encourage- 

 ment that he gave me while I was doing this work as one of his students, and I am also 

 indebted to Professor C. 0. Whitman, to the Hon. George M. Bowers, and to Professor 

 H. C. Bumpus for the many courtesies received while at Woods Hole. 



TECHNIQUE. 



For the preservation of the very young larvae a one quarter saturated solution of 

 picric acid, with 2% of sodium chloride added, gave good results. Erlicki's fluid with the 

 same addition, and j% osmic acid followed by Erlicki's fluid, did fairly well for scyphis- 

 tomas, but the best specimens obtained were those killed in the following mixture : 

 10% solution copper sulphate 100 c. c. 



saturated solution corrosive sublimate 10 c. c. 



As soon as they were killed, the specimens were placed in 5% bichromate of potassium 

 and left there until hardened, after which they were washed in 35% alcohol containing a 

 trace of hydrochloric acid and preserved in 70% alcohol. Excellent preparations of the 

 medusae were obtained by this same method, and Flemming's fluid also gave good results. 



