Rev. T. HIncks 07i the History of the Hydroida. 391 



the opportunity of observing the same mode of development in 

 Campariularia neglecttty Alder, and have little doubt that it is 

 far from uncommon amongst the Hydroida. In the month of 

 June I obtained a fine colony of the Campanidaria bearing a 

 full complement of polypites and also a considerable number 

 of branches, carrying at their extremities the planuloid exten- 

 sions of the coenosarc described by Allman (PL XX. fig. 4, a;). 

 I am inclined to think that they were of greater length than 

 those of ScMzocladium, but in other respects exactly resembled 

 them. I did not actually witness the liberation of the frustule, 

 but in one case at least a constriction was very apparent a little 

 within the chitinous tube of the stem, at which point no doubt 

 separation would ultimately have taken place. 



I confess that, with great deference for Prof. Allman's 

 opinion, I am unable to accept his genus ScMzocladium, which 

 seems to rest on a single character, the development of fission- 

 frustules in a certain way — a character which, there is reason 

 to believe, may have a wide range amongst the Hydroida. 

 There seems to be nothing peculiar in the trophosome of his 

 zoophyte but the presence of the frustule-bearing branchlets ; 

 there is nothing in his account or figure of it, apart from this 

 character, to indicate that it is even specifically distinct from 

 known forms of Ohelia or Campanularia. 



The observation of reproduction by fission in Camp, neglectaj 

 and its probable occurrence, as recorded by Allman himself, 

 in Corymorpha^ tend to show that scMzocladism may be a 

 common element in the reproductive history of the Hydroida, 

 and that it therefore cannot be the peculiarity of a genus. 

 The frustule with its branchlet is hardly likely to exhibit any 

 morphological peculiarities that will serve the purpose of the 

 classifier. It presents the same character in Camp, neglecta as 

 in Allman's Hydroid, which is probably an Ohelia. 



Prof. Allman has made a most important and interesting 

 addition to our knowledge of the modes of reproduction amongst 

 the Hydroida ; but I venture to think that he himself will 

 hardly care to retain the new genus. 



IV. Cladonema radiatum, Dujardin : the Planohlast, 

 [Plate XXI. fig. 6.1 

 Through the kindness of Dr. Hudson, of Clifton, I have 

 had the opportunity of examining during the past summer, for 

 the first time, the planoblast of Cladonema radiatum^ which he 

 had taken at Watermouth near Ilfracombe. I was surprised 

 to find the tentacles unbranched and furnished with only one 

 suctorial appendage. In this state they bear a very close re- 

 semblance to those of Clavatella, the only important difference 



