TUBICLAVA. 255 



the influence of the sea water. On tliose buoys which lay further down the river no Cordi/Iophora 

 was found, but in its stead abundance of truly marine hydroids.' 



The observations made by Kircheni)aucr on the change of life as seen in the forms which 

 successively show themselves on the buoys in proceeding from the sea at the mouth of the river 

 upwards into tiie fresh water, arc full of interest and significance. 



TUBICLAVA, Allman. 



Name. — From Tubus, a tube, and Clava, a genus of hydroids ; in allusion to the form of the 

 trophosome, which resembles a Clava invested by a tubular perisare. 



TROPHOSOME. — IlTDKOPnTTON consisting of a conspicuous htduocaulus in the 

 form of simple or branched stems, and of a creeping filiform htdborhiza ; the 

 whole invested by a chitinous peuisarc. Htdranths claviform, with scattered filiform 

 tentacles. 



GONOSOME.— [GoNOPHouES adelocodonic, borne by the hydranth at the proximal 

 side of the tentacles.] ?' 



It was in one of the shallow rock pools left Ijy the retiring tide at Torquay that I obtained 

 the trophosome of a hydroid which resembled that of a minute Clava in all respects, except in 

 the fact that the hydranths were supported on conspicuous though simple stems, which were 

 invested by a distinct perisare. 



The specimens were unfortunately destitute of gonophores, but the trophosome brought to 

 my mind a very similar hydroid which I had obtained several years previously on the shores of 

 Dublin Bay, and in which the gonosome was present. 



The Dublin Bay specimens, like those of Torquay, had a developed hydrocaulus, which was 

 invested by a perisare. The gonosome was exactly that of Clava inulticonils, consisting of 

 similar clusters of gonophores grouped round the base of the hydranth-head. I regarded it, 

 indeed, at the time as a mere variety of Clava multicornis,\\\ which the hydrocaulus had taken on 

 an unusual development, and I thought little more about it until the occurrence of the Torquay 

 hydroid brought it to my memory. 



While I consider the Torquay hydroid with its well-developed hydrocaulus as generically 

 distinct from Clava, I am now disposed to regard it as identical with the hydroid of Dublin Bay. 

 If so, the gonosome is known, and we have all the data necessary for a complete generic 

 diagnosis. 



' Kirchenpauer, " Die Seetonnen der Elbmundung." ' Abhandl. uaturwiss. Vereine in Hamburg,' 

 iv Band, 1862. 



- See the general remarks on the genus given below. 



