<308 ox A CUEIOUS IXSTANCE OF SYMBIOSIS, 



species, wliicli is described as retracting itself when disturbed 

 Avitli extreme rapidity into its tube. 



Note ox a cueious instance of Symbiosis. 



By William A. Haswell, M.A., B.Sc. 



In the June before last I obtained with the dredge off Thursday- 

 Island, in a depth of four or five fathoms, specimens of a branching 

 species of Cellepora, which was dotted over with small red specks. 

 On examining these more minutely, I found each to consist of a 

 minute Acimid lodged in a cylindrical pit excavated in the 

 substance of the polyzoarium and projecting, when expanded, 

 about a quarter of an inch from the surface of the latter. Each 

 of the pores is about a twentieth of an inch in diameter ; they 

 are cylindrical and tolerably smooth, and in most cases the orifices 

 are furnished with a low projecting rim. When they are traced 

 backwards into the substance of the CJellepora two are frequently 

 found to unite, and very often they eventually open into the 

 cavity occupying the centre of the thicker branches. They very 

 often extend in this way through a distance many times greater 

 than the length of the ActuiiditseU, and, as the latter is provided 

 with no means by which it can retract itself into the interior, 

 this long canal must be the result of the simultaneous growth of 

 the little anemone and the Cellepora in which it is lodged. 



This singular phenomenon is specially interesting on account 

 of the light which it throws on the structure of some very 

 problematical-looking species of Bryozoa, one of which I described 

 not long ago under the name of Sj)li(Broporafossa.^ In this species 

 the bryozoarium is spherical, slightly compressed, one pole being 



* Mr. "Waters, whose authority on the subject of Bryozoa is probably as 

 f^a'eat as that of any living zoologist, regards the form of the cells as not 

 being sufficiently distinctive to justify the separaticn of this species from 

 Cellepora. 



