44 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 







contains a rich supply of ganglion cells and is considered by him to be 

 the centre of the nervous system of the medusa. A close comparison 

 cannot be drawn with Chary bdea in this matter, however, since Charybdea 

 has nothing to correspond with the "outer" and "inner" sensory pits. 

 Moreover, the endodermal tract is not found encircling the canal of the 

 sensory club, nor could I trace fibres passing from it through the 

 supporting lamella into the fibres of the nerves. 



Glaus has figured (78, Taf . V, Fig. 45, Fb) a small bundle of fibres in 

 the stock of the sensory club lying between the endoderm cells of the 

 canal and the supporting lamella. The same bundle is found in both 

 Charybdea and Tripedalia and can be traced in cross-sections up the 

 stalk to a point which must correspond with that at which the endoder- 

 mal tract is seen in Fig. 52. Downwards it can be traced only as far as 

 the entrance of the stalk into the knob of the club where it invariably 

 becomes lost to view. According to Hesse ('95, p. 427) Schafer found 

 under the endoderm cells of the whole stalk of the marginal body a 

 fibrous layer like that under the endoderm cells which he refers to 

 slender processes from the cells of the crystalline sac. Although Hesse, 

 as we have seen, finds the layer more limited in extent than Schafer 

 gives it, and does not trace it to the same source, the observation of 

 Schafer seems to me worthy of mention here, inasmuch as the trend of 

 the fibrous bundle under the endoderm cells of the stalk in Charybdea 

 and Tripedalia suggests quite strongly that the fibres come from the 

 crystalline sac, as Schafer thought to be the case in his medusa. 



Besides the radial ganglion situated in the course of the nerve ring 

 at its four perradial points there are four other similar ganglia 011 the 

 subumbrella. These lie in the interradii, at the four lowermost points of 

 the nerve's course, and undoubtedly send off nerves into the pedalia at 

 whose bases they are situated. F. Miiller ('59), whose work was not 

 accessible to me, is quoted by Glaus as recording two ganglia opposite 

 the base of each pedalium which gave off a great number of nei'ves 

 partly into the velarium, partly into the tentacles. Glaus observed 

 nothing of the kind in Charybdea and states that even the interradial 

 ganglia do not exist. 



That they do, however, is shown without doubt in sections of both 

 C. Xaymacana and Tripedalia, but nerves to the velarium or to the ten- 

 tacles I was unable to find. 



On the two sides of each frenulum and of each suspensoi'ium are 

 found sub-epithelial ganglion cells in greater numbers than elsewhere on 



