46 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



to some slight extent. A similar form from Hammerfost 

 has been described by K. Bonnevie under the name of 

 T. obliqua (Zeitschr. wiss. Zool. ; Jahrg. 63 ; 1898 " Zur 

 Systeniatik der Hydroiden ") and figured amongst the 

 Hydroida of the Norske Nordkavs-Expedition, 1896-8 ; 

 Christiania, 1899. This new species was founded for a 

 single specimen, which Froken Bonnevie tells me was a 

 female. Gr. Swenander has since found similar gonophores 

 produced by colonies, many of the zooids of which bore 

 the normal non-tentaculate gonophores of T. indivisa (Det 

 Kongl. Norske Vid. Selsk. Skr. 1903; Trondhjem, 1904; 

 No. 6. " Uber die Athecaten Hydroiden des Drontheims- 

 f jordes "). He therefore regards Bonnevie's species as a 

 variety of T. indivisa. 



None of the female specimens from this rock at Port 

 St. Mary that I have examined have failed to show the 

 presence of the tentacle on most of the gonophores, though 

 in one case at least it is absent from a few of them ; and 

 in addition to this it is unusual for their blastostyles to be 

 long and pendulous as is usual in T . indivisa. Pendulous 

 female blastostyles have occasionally been seen, however, 

 and occurred in Bonnevie's original specimen ; they are 

 a constant feature of the male hydranth. There are also 

 certain minor differences to be seen between sections of 

 the gonophores of this form and of the normal T . indivisa. 

 The female shows a single radial canal instead of four — 

 a feature obviously correlated with the presence of the 

 single large tentacle to the base of which the canal runs, 

 there communicating with the large endodermal cavity 

 of the tentacle ; whilst the male shows no radial canals 

 (or tentacles) at all, but does shoAv — what the normal 

 T . indivisa apparently does not — conspicuous sterile cells 

 in the outer layers of sperm, these cells often bearing 

 delicate processes that pass inwards towards the spadix, 



