86 THE MEDUSAE. 



much too large, — an error due to the contracted condition of the preserved 

 material. The sense organs themselves (PL 18, fig. 7) are of the usual type, 

 each containing two or three otoliths. They are situated on " auditory 

 pads "; thickenings of the nerve ring, consisting of spindle-shaped ectoderm 

 cells some at least of which bear bristles, though most of the latter are 

 destroyed by preservation ; and, as in all members of this genus, each 

 octocyst is connected with a long otoporp containing nematocysts (PL 18, 

 fio - . 7, op.). At their distal ends these structures are bounded by cap-like 

 series of columnar ectoderm cells. 



Gastro-vascular system. — The stomach is flat, its ventral wall without any 

 trace of such folds or ridges as Haeckel ('81) has figured for P. pantheon. 

 Indeed, I doubt whether such a conformation is anything more than the 

 result of alcoholic contraction. The mouth is surrounded by a simple and 

 very distensible lip. In life it is often opened so wide as to occupy half the 

 area of the stomach, or again contracted, as in PL 18, fig. 2. There are 

 no traces of gastric pockets (PL 18, fig. 4). The canal system is typical of the 

 genus, both peronial and ring canals being well developed (PL 18, fig. 4). 



Gonads. — Since the conformation of these structures has been used by 

 both Haeckel ('79, '81) and Maas ('93) as a specific criterion in Pegantha, it 

 is fortunate that I can describe them from life. Haeckel ('79) describes them 

 in P. martagon as neither folded nor incised, but while this is true for 

 young specimens in which they are simple sac-like structures (PL 18, fig. 5), 

 in larger ones they are more or less lobed and irregular (PL 18, fig. 6), though 

 never definitely and regularly subdivided as in P. biloba and in P. dactyletra 

 (Maas, '93). There is one important structural feature of the gonads in 

 this, as well as in the other species of the genus which I have examined, 

 mentioned neither by Haeckel nor Maas probably because of the methods of 

 preservation of their specimens. This is that the gonad is not a sac with 

 large open cavity, but is supported, and its convexity chiefly caused, by a 

 rounded prominence of the gelatinous substance of the disc (PL 18, fig. 8, 

 g. pn.), just such as is present in the corresponding location in Sohnissus 

 marshaM and in S. incisa (p. 68). These prominences are absent in young 

 specimens and appear, in both sexes, only with the formation of the gonads. 

 They do not extend into the subdivisions of the gonads, but occupy their 

 central region only. 



This Bpecies is colorless ; the bell hyaline, the endodermal structures opaque. 



Pegantha martagon is widespread, having been taken in the Indian Ocean 



