INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 655 



If tliis be the case, Limnocodium will hold a position iutermetliate 

 between the Leptomeclusce and the TrachomedusEe ; but as the greatest 

 systematic importance must be attached to the structure and origin 

 of the marginal vesicles, ils affinity with the Leptomedusa3 must, 

 Professor Allman considers, be regarded as the closer of the two. 



Professor Lankester * considers that the animal is one of the sub- 

 class Hydromedusas or Medusfe craspedotae, and presents the common 

 characters of the order Trachomedusfe (as distinguished from the 

 Narcomedusas) in having its genital sacs or gonads placed in the 

 course of the radial canals. It agrees with all Tracholina2 (Tracho- 

 medusai and Narcomedusa)) in having endodermal otocysts, and it 

 further exhibits the solid tentacles with cartilaginoid axis, the centri- 

 petal travelling of the tentacles, the tentacle rivets (Mantelspangen), 

 the thickened marginal ring to the disk (Nessel ring) observed in 

 many Tracholinre. 



Amongst Trachomcdusae, it finds its place in the Petasida), which 

 are characterized as " Trachomedusfe with four radial canals, in the 

 course of which the four gonads lie, with a long tubular stomach and 

 no stomach-stalk." 



Amongst Petasidaa it is remarkable for the great number of its 

 tentacles, which are all solid ; and for its very numeroiis otocysts. 

 Further, it is remarkable among all Hydromedusfe (velato Medusas, 

 that is, exclusive of Charyhtlcea) for the fact that centrifugal radiating 

 canals pass from the otocysts into the velum, where they end ccecally." 



The characters of the genus are given, and it is pointed out that 

 the presence of velar otocystic canals constitutes the chief peculiarity 

 of the genus, and may necessitate the formation of a distinct family 

 or sub-order for its reception. The sole character which can be 

 given as specific over and above the generic characters is that of size. 

 The diameter of the disk does not exceed one-third of an inch. 



It is exceedingly difficult to trace the introduction of the animal 

 into the tank in the Regent's Park, since no plants have been recently 

 (within twelve months) added to the lily-house, and the water is run 

 off every year. Probably a few specimens were last year or the year 

 before i)reseiit in the tank, and have only this year multiplied in 

 sufficient abundance to attract attention. Clearly this Medusa is a 

 tropical species, since it flourishes in water of the high tem])craturo 

 of DO^ Falir. Mr. Sowerby has observed it feeding on JJaphnia, 

 which abounds in the water with it. 



Professor Lankester sul)sequeutly published t a fuH prelirainaiy 

 memoir of the animal, illustrated by woodcuts and jdatcs, in which ho 

 shows that, contrary to the conclusion of Professor Allman, the ten- 

 tacles of Limnocodium do resemble those of the Tnu-hyliuu IMedusa) 

 in their insertion and in the possession of true (tliough rudiniuiitury) 

 pcronia, also that the statement that the so-called litliocysts or 

 marginal bodies have essentially tlie saniu structure as those of 

 Tracliyline IMcdusai (being modified tentacles with an endodonnal 

 axis) is warranted by their develoinnental history. Consequently ho 

 adheres to the original determination of the affinities of the new 

 * L.K^'. fit., J.. U7. t ' <i"iiil. Joiini. Mi.T. Sci.,' xx. (ISSO) p. :r.|. 



