262 Miscellaneous. 



large size. The coiling of the radial canals is evidently insufficient 

 for the unfolding of the gonads ; the latter therefore themselves 

 become closely twisted once more, and thereby acquire their striking 

 breadth on the subumbrellar surface and on the sides of the canals. 



The living Medusae were of hyaline transparency, with a pale 

 yellowish tinge ; only the tentacles and the margin of the bell 

 appeared slightly milky, the former owing to the innumerable 

 nematocysts, the latter in consequence of the tracts of the circum- 

 ferential muscle. The yellowish-brown bands of the gonads showed 

 plainly through the tissues. 



If we now consider the systematic position of our Medusa, it may 

 be most advisable to test the diagnoses of Hackel's exhaustively 

 worked-out system, with reference to their a])plicability to this 

 freshwater form. 



Hackel divides the Craspedota into Anthomedus*, Leptomedusse, 

 Trachomedusoe, and Narcomedusa). The two latter divisions do not 

 here concern us. Neither is it necessary to consider the Antho- 

 medusas, for only in the Leptomeduste do the gonads lie in the walls 

 of the radial canals. 



Of the four subdivisions of the Leptomedusa3 it can only be a 

 question of the Thaumantidae or iEquoridaj, for in the case of the 

 Cannotidai the gonads are plumose branches of the radial canals, 

 while in the Eucopidoe they are vesicle-shaped evaginations there- 

 from. 



While, however, the ^quoridai further " always possess marginal 

 vesicles," which are wanting in our Medusa, there only remain the 

 Thaumantidie, in which the gonads form frill-like folded bands 

 along the radial canals, marginal vesicles are always absent, ocelli 

 usually present. 



If we construct a synoptical survey of the genera which belong 

 to this subdivision, we get the following table : — 



4 radial canals and 4 gonads, h. 

 8 radial canals and 8 gonads (Melicertida;). 

 16 radial canals (Orchistomidoe). 

 h. 4 or 2 tentacles. 

 8 tentacles. 

 16 or more tentacles, c. 



c. No marginal bulbs nor cirrhi. d. 



Between the tentacles, bulbs and cirrhi. 



d. Independent mouth and atrium, ]io gastro-geuital 

 cross. — Thaumantias. 

 Mouth and atrium obliterated, a gastro-geuital 

 cross. — Staurostoma. 



According to this table we should arrive at the genus Thauman- 

 tias for our Medusa. The four species placed here by Hackel, 

 however, have frilled and very variable oral lobes, which does not 

 agree with what we find in this freshwater form. 



It follows, therefore, that if we are to find a place for the medu- 

 soid form only, as I am compelled to do, a new genus must be 

 intercalated. If, when the hydroid is discovered and the mode of 

 development understood, a new position should be found for the 

 creature, it can be transferred at any time to its proper place. In 



