CLADONEMA RADIATUM. 359 



grounds, and the true tro[)liosome has been entirely overlooked by the learned Belgian zoologist. 

 Van Beneden's description of the medusa, however, is a valuable contribution to our knowledge 

 of the species. He has shown that the marginal tentacles are at first comparatively simple, and 

 that their ramification increases up to a certain point with the age of the medusa — statements 

 which I can confirm from my own observations. 



The three smooth appendages which are given off" near the base of the tentacle serve the 

 medusa as organs of attachment, the terminal capitida of these appendages having the power of 

 adhering, sucker-like, to any surface to which they may be applied, and the little medusa may be 

 often seen attaching itself by means of them to the sides of the glass jar in which it is confined. 



It is impossible to grow tired of watching this beautiful little medusa ; sometimes while dashing 

 through the water with vigorous systole and diastole, it will all at once attach its grapples to the 

 side of the vessel, and become suddenly arrested in its career, and then after a period of repose, 

 diu'ing which its branched tentacles are thrown back over its umbrella, and extended into long 

 filaments which float, like some microscopic seaweed in the water, it will once more free itself 

 from its moorings and start off with renewed energy. 



When the medusa is in the act of swimming, the tentacles are contracted and curved 

 upwards round the margin of the umbrella. In this state the smooth appendages of attachment 

 undergo little or no contraction, but the nodulated appendages are strongly contracted, and 

 assume the appearance of short thick clubs. 



The development of Cladonenia is through planula;, as has been shown by Krohn. Dujardin 

 has also seen the stauridioid trophosome developed from the egg of the medusa, but he over- 

 looked the intermediate stage of planula. 



Dujardin has noticed a retroversion and ultimate absorption of the umbrella near the time 

 when the ova are about to be deposited, and this observation has been, according to Mr. Ilincks, 

 confirmed in great part by Mr. Holdsworth. ' The phenomenon may be compared to what has 

 been noticed above in Syncoryne pulchella (see p. 203), while similar observations have been 

 made liy Hincks and otliers on the medusa3 of Podocoryne and of Tarris (see Hiucks, op. cit.. 

 Introduction, p. xxix). 



Dujardin informs us that he has seen the ova of Cladonema adhering to the glass vessel in 

 Avhich the medusae were confined, and he states that he has seen the medusa remove the ova 

 from the cavity of its manubrium by means of its marginal tentacles, which are introduced into 

 the mouth for this purpose; while he further describes these tentacles as employed in glueing the 

 ova to the glass — statements which there can be little doubt are founded on some deceptive 

 observation. 



