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 Meduste 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 HUckel's exhaustively 

 worked-out system, with reference to their applicability to this 

 freshwater form. 



Hacked divides the Craspedota into Anthomedusaj, Leptomedusa;, 

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

 here concern us. iSTeither is it necessary to consider the Antlio- 

 medusai, for only iu the Leptomedusa) do the gonads lie in the walla 

 of the radial canals. 



Of the four subdivisions of the Leptomedusa? it can only be a 

 question of the Thaumantidae or .^quoridai. for in the case of the 

 Cannotidae the gonads are plumose branches of the radial canals, 

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

 from. 



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

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

 Thaumantida5, 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 : — 



A radial canals and 4 gonads, h. 

 8 radial canals and 8 gonads (Melicertida;). 

 16 radial canals (Orchistoniida;). 

 h. 4 or 2 tentacles. 

 8 tentacles. 

 IG or more tentacles, c. 



c. Xo marginal bulbs nor cirrhi. d. 



Between the tentacles, bulbs and cirrhi. 



d. Independent mouth and atrium, no gaslro-genital 

 cross. — Thaamantias. 

 Moutli and atrium obliterated, a gastro-gonital 

 cross. — Staurostoma. 



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

 Has for our Medusa. The four species placed here by Ilackel, 

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

 agree with what we tind in tliis freshwater form. 



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

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

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

 development understood, a new [)osition should be found for the 

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



