PEGANTHA MARTAGON. 85 



between diameter and height varies, and in life was constantly changing, 

 with changes in the state of contraction of the Medusae. Above the line 

 of insertion of the tentacles the surface of the bell is smooth, showing 

 neither nematocyst warts nor radial ridges. Sculpture is, however, present 

 on the marginal lappets, there being a slightly marked ridge in the median 

 line of each lappet, and fainter ones in the lines of the otoporpae, all being 

 much less prominent in this species than in P. triloba. The marginal lappets 

 are ovate in outline, rather longer than broad, the incisions between them 

 deep, and the peroniae correspondingly short (PI. 18, fig. ^). In adults the 

 peroniae are covered by the gelatinous substance of the adjacent marginal 

 lobes. 



The number of lappets and tentacles is variable, as is usual in Pegantha, 

 the largest number observed being thirteen, in a specimen 14 mm. in 

 diameter, the smallest nine, in specimens 5 and 16 mm. in diameter. In 

 one small specimen, 9 mm. in diameter, from Station 4646, in which the 

 gonads have not yet appeared, one of the twelve tentacles is much smaller, 

 and evidently of more recent formation, than the others (PI. 18, fig. ^) ; but 

 in large specimens in which the gonads are formed I have not found any 

 trace of the development of interstitial tentacles. It appears, then, that the 

 full number of tentacles in this species is early attained and does not con- 

 tinue to increase with growth. The tentacles are of the usual narcome- 

 dusan type, about as long as the bell diameter, and in life carried trailing, 

 or recurved into the bell cavity. The only feature in which the present 

 specimens differ markedly from Haeckel's description is in the number of 

 octocysts. Haeckel ('79, p. 332) states that there are from thirteen to 

 fifteen of these organs on each marginal lappet, but the greatest number 

 which I have found in any lappet is nine, while most lappets have only 

 from six to eight. It is, however, questionable whether Haeckel's counts 

 of the octocysts are reliable, since he states that his description of this 

 species was taken from strongly contracted alcoholic specimens ; and I find 

 from my own experience that it is almost impossible to count these organs 

 on such material. Even if such a difference does exist in different groups 

 of individuals, it does not seem to me of much systematic importance, 

 because the number of octocysts increases with growth, and is variable in 

 the different lappets of any one individual. Renewed examination of the 

 specimens from the Maldives has convinced me that the number of octocysts 

 which I recorded for them, twenty-five per lappet, was an error, being 



