278 ' ENDEAVOUR " SCIENTIFIC RESULTS. 



Sertularia abietinoides, Hutton, Trans. N.Z. Inst., v., 1872, 

 p. 257. Id., Coughtrey, Trans. N.Z. Inst., vii., 1874, 

 p. 285, pi. xx., figs. 16, 18-20 ; Id., Coughtrey, Trans. 

 N.Z. Inst., viii., 1875, p. 300. Id., Pfeffer, Erg. d. 

 deutscher Polarexp., ii., 1892, p. 116. 



Most specimens of S. elongata can be definitely assigned to 

 either the large or the small variety, though intermediate 

 forms occur. The two varieties were by Lamouroux named 

 respectively 8. elongata and 8. scandens, and by Lamarck 

 8. lycopodium and 8. millefolium. I have referred to this 

 species in Part I 1 , and it has been so often described that 

 little need be said of it here. No operculum has been 

 detected, consequently in the system of classification pro- 

 posed by Levinsen it is excluded from the genus. The 

 hydranths have about 16-18 tentacles. 



Billard, in his Revision of part of the British Museum 

 Hydroids, (Ann. Sci. Nat., Zool., (9), xi., 1910, page 22), has 

 described some colonies which he found among clusters of 

 Sertularia elongata from Australia in the Bowerbank Collection, 

 and which, owing to this association, he has hesitated to 

 describe as a new species, though they differ from 8. elongata 

 in the opposite ramification, in the opposite position of the 

 cauline hydrothecse, in the number of the marginal teeth, as 

 well as the form of the hydrothecse, in the presence of an 

 unpaired hydrotheca on the proximal part of each pinna, 

 and finally in the totally different form of the gonangia 

 Billard thinks it just possible that this may be a curious case 

 of sexual dimorphism. 



I do not think this theory tenable, for several reasons. In 

 the first place, of course, is the fact of the complete unlikeness 

 of the two species in every detail. This of itself should, I 

 think, be considered conclusive against any evidence short 

 of tracing the two to the same hydro rhiza. Then it must be 

 remembered that 8. elongata is an extremely common species, 

 the most abundant indeed on the southern Australian coast, 

 and it is scarcely credible that one of its sexual forms should 

 have hitherto escaped observation except in this single 

 instance, especially as the difference in the ramification 

 would be apparent to the naked eye. 



Another important consideration is that this is not an 

 entirely isolated form, but is a representative of a group of 

 species, all of which agree in their most characteristic 

 features. Billard refers to one of these 8. huttoni, Mark- 

 tanner-Turneretscher and to this may be added 8. acantho- 

 stoma, Bale, and 8. insignis, Thompson. 



1. Bale Biological Results "Endeavour," ii., 1, 1914, p. 9. 



