72 



ANTHOZOA. 



Fig. 33. 



all the lamellae bordered with white filaments ; and others describe them 

 as all bearing clusters of ovules. In these instances it would seem that 

 the sexes are distinct, in one case the animal being male, in the other 

 female. The ovules have been seen to escape by the mouth ; and this 

 therefore appears to be the general mode in all the Actinoid polyps. 



(157.) At the point 

 where the ovigerous la- 

 minae reach the tentacles 

 a membrane is observable, 

 which assumes the shape 

 of a funnel when the ani- 

 mal retires into its shell ; 

 and at the open end of the 

 funnel the membrane is 

 seen to fold outwards and 

 become continuous with 

 the calcareous tube (fig. 33, 

 1, 6) ; its inner surface, in- 

 deed, is prolonged under 

 the form of a thin pellicle 

 over all that part of the 

 interior of the tube which 

 is inhabited by the polyp, 

 terminating at a kind of 

 diaphragm composed of 

 the same hard substance 

 as the tube itself. The 

 remains of these dia- 

 phragms are found in the 

 interior of old tubes at va- 

 rious distances from each 

 other. 



(158.) The funnel-shaped membrane does not terminate suddenly 

 at its point of junction with the calcareous tube ; the latter, indeed, 

 is a continuation and product of the first, the calcareous substance 

 being evidently deposited in this gelatinous membrane in the same 

 manner as phosphate of lime is deposited in the bones of very young 

 animals, changing its soft texture into hard, solid substance. The 

 manner therefore in which this tube is formed cannot be compared 

 to the mode of formation of the shells of mollusca : in the latter case it 

 is a secretion from the skin, an epidermic product ; but in these poly- 

 paries there is a real change of soft into solid substance, which is 

 effected gradually, but not deposited in layers. 



(159.) When the tube has acquired a certain height, the animal 

 forms the calcareous horizontal plate which unites it to those around ; 



Anatomy of Tubipora. 1. a, Polyp partially expanded ; 

 b, flexible extremity of the tube ; e, ovigerous laminte ; 

 f, calcareous portion of the tube. 2. 6, Expanded extremity 

 of the tube, still uncalcified ; c, polyp retracted ; d, inflected 

 membrane embracing the neck of the polyp. 3. Ovarian 

 lamina detached. 4. Development of young : a, horizontal 

 stage ; 6, c, growing offspring. 



