624 EDWARD POTTS. 



of the figures of this medusa show, as described in the 

 'American Naturalist/ the eight tentacles, one at the ter- 

 mination of each radial caual^ and the others alternating 

 with them ; the latter figure also shows at the centre^ as in 

 an optical section, the quadrate character of the mouth parts 

 of the manubrium. The polyp of this species was found in 

 two localities in the neighbourhood of Philadelphia, Penn- 

 sylvania, U.S.A., in Jauuary, 1885, and studied more or 

 less continuously for twelve years before the medusse were 

 detected in August, 1897. The figures of the medusa here 

 given (figs. 13 and 14) were drawn by Dr. J. Percy 

 Moore, of the Biological Department of the University of 

 Pennsylvania, from medusae placed by myself in a very dilute 

 aqueous solution of formalin some time in August or 

 September, 1897; and, although possibly somewhat shrunken, 

 they correspond very closely with my remembrance of them 

 when fresh, and with my description published in the 

 ' American Naturalist ' of December in that year. These 

 medusas have as yet only been seen as they were developed 

 from the hydroids in comparatively small culture-jars at my 

 home, where they were quickly lost sight of amongst water- 

 plants kept floating at the surface. Under these circumstances 

 none probably reached an age of more than two or three days, 

 and can only be safely compared with figs. 5 and 6, PI. 35, 

 supposed to be mature, by experts familiar with similar types 

 of marine medusa. During several weeks of the year 1897, 

 and occasionally during the two following years. Dr. Daven- 

 port, Prof. Cheyney, with myself and some others, were 

 cognisant of the budding and liberation of several medusa). 



I have felt an especial pleasure in finding, as represented 

 in figs. 15 and 16, PI. 36, two rough drawings (the latter by 

 camera lucida) among my papers dated September 5th, 1897. 

 They represent sketches made, during the afternoon and 

 evening, of the same medusoid bud at an early stage of its 

 development ; and, under date of the 7th of the same month 

 in my letterpress-book, I found copies of the following letter 

 addressed to Dr. C. B. Davenport, referring to the same 



