HALOCORDYLE COOPERI. 209 



Note on the Variation in the Arrangement of 

 the Capitate Tentacles in the Hydroid, Halo 

 cordyle cooperi Wan-en. 



By 



Ernest Warren, D. Second., 



Director of the Natal Government Museum. 



In the description of this new species in the ' Annals of the 

 Natal Government Museum,' vol. i, part 1, it was pointed out 

 that the airangement of the capitate tentacles exhibited 

 considerable variation. 



According to AUman,^ the genus Pennaria is charac- 

 terised by the hydranth having twenty to thirty capitate 

 tentacles scattered irregularly over the sides of the body, 

 while the genus Halocordyle has about twelve capitate 

 tentacles arranged in two verticils of about six in each. 

 Typically H. cooperi possesses two alternating verticils of 

 four tentacles, but the species exhibits marked variations in 

 the arrangement, and it was thought that a statistical investi- 

 gation into the matter might prove of interest. 



It is unfortunate that the hydroid is comparatively rare. 

 The coast of Natal has been searched diligently at different 

 places on a number of occasions, but only forty-two colonies, 

 and some of these were in poor condition, have been found 

 altogether. As it is improbable that any considerable number 

 will noAv be obtained, I will give the results, although the 

 amount of material is not sufficient for a strict analysis. 



' ' A Mouoi^rapli of the Gymnoblastic or Tubularian Hydroidss." Part 

 II, pp. 304, 367. 



