36 Proceedings of the Boyal Physical Society. 



(see PL I., Fig. 1) a polype is always placed at each angle 

 of the meshes. Of course, in order to form a closed mesh, 

 besides branching, union must have taken place between 

 the growing tips of two stolons, but I have not been able 

 to find traces of this in any of my specimens, and conse- 

 quently I am unable to say whether the union takes place 

 at the base of a polype or between two polypes. 



In one or two cases I found the growing tips of stolons 

 projecting beyond the edges of the stone to which the colony 

 was attached, and one of these had three small polypes on it, 

 thus showing how a colony projecting freely upwards might 

 be developed from an incrusting form. 



The Polypes vary somewhat in form, but are always more 

 or less dome-shaped or conical, with the top truncated. In 

 a couple of cases the polypes upon one surface (probably the 

 lower one) of a stone were much lower than those upon the 

 other surface. Fig. 5 on PL I. shows the most usual shape 

 of polype in profile view. It rises very considerably above 

 the surface of the stone, even in this contracted condition, 

 and doubtless attains a much greater height when living 

 and expanded. 



I did not succeed in getting any of my colonies to ex- 

 pand ; but Mr Gosse describes his living polypes as having, 

 when expanded, a height of \ of an inch, and a diameter 

 of yV of an inch. The usual size of my retracted speci- 

 mens is 2 mm. in diameter at the base, and 2 to 2*5 mm. 

 in height; but there are a few polypes which have partially 

 expanded on being placed alive in alcohol, and these show 

 above the body shown in Fig. 5 a colourless zone 1 mm. 

 high and 1 mm. in diameter, and terminating in the mouth 

 opening surrounded by the circle of tentacles, which attain a 

 length of about 2 mm. Hence my partially expanded polype 

 measures, including tentacles, about 5 mm. in height. The 

 examination of such expanded polypes shows that in the con- 

 tracted specimens the upper part of the body has been 

 entirely retracted, and is not visible externally. 



The upper end of the contracted polypes shows a truncated 

 rounded surface with a central aperture (see PL I., Fig. 6) 

 surrounded by eight equal-sized and fairly regular lobes. 



