rOLYPIFERA. 



47 



the interior of which may be observed a ve- 

 sicle that soon becomes organised into nu- 

 merous cells, which constitute the vitelline 

 mass exactly as in the last case. But, arrived 

 at this point, the vitelline mass becomes tu- 

 berculated, assuming the appearance of a rasp- 

 berry, and, instead of a single vitellus, it is 

 found to be an agglomeration of several, each 

 of which contains in its interior a Purkingean 

 vesicle from which a young individual is pro- 

 duced, which is of a totally different form from 

 its parent and covered with cilia; by the aid of 

 which it swims freely about in search of a 

 locality where to fix itself. This form of re- 

 production will, however, be more particularly 

 noticed in describing the Sertularian Polypes. 



Fifth mode, by free gemination and ova com- 

 bined. This last form of the reproductive 

 process is merely a combination of two of the 

 preceding, propagation being effected by the 

 development of a free gemma, in the interior 

 of which there is formed a divided vitellus. 

 In this case a free embryo becomes organised, 

 and takes the form of a young Medusa, accord- 

 ing to the second mode described above, in 

 the interior of which is contained an ovum 

 with a multiple vitellus, from which numerous 

 ciliated embryos are produced, as in the Ser- 

 tidaria geniciilata hereafter to be noticed. 



Tubiporidce. The polypary of the Tubi- 



Fig. 52. 



Tubipora musica. 



pora (fig. 52.)consists of several stages of cy- 

 lindrical tubes placed parallel to each other, or 

 very slightly diverging. These tubes are sepa- 

 rated from each other by considerable intervals, 

 but mutually support each other by the inter- 

 position of external horizontal plates formed 

 of the same dense substance as themselves, by 

 which they are united together, so that a mass 

 of these tubes exhibits an arrangement some- 

 thing like that of the pipes in an organ ; 

 whence the trivial name musica by which the 

 species is distingu : shed. From the upper 

 ends of these tubes the polypes are protruded, 

 and being when alive of a bright grass green 

 colour they contrast very beautifully with the 

 rich crimson of the tubes they inhabit. The 

 mouth* of the polype is suspended in the 

 centre of the tube by means of the soft mem- 

 brane : it is surrounded with eight tentacula, 

 the margins of which are fringed with two or 



' * Anatomie du Tubipore musical par Mons. La- 

 mouroux. Zoologie de Quoy et Gairnard, Voyage 

 de 1'Uranie. 



three rows of fleshy papilla?. Beneath the 

 opening of the mouth is the stomachal saccu- 

 lus, around which arise the eight ovigerous 

 filaments. Those filaments near their origin 

 are loose and floating, but lower down they 

 become connected with the soft membrane 

 (jig. 53. 1, 2, d), with which the tube is lined, 



Tubipora musica. 



1, 2, longitudinal sections ; 3, portion of the poly- 

 pary, showing the connecting stage. 



a, membranous collar, continuous with the tube ; 

 b, calcareous tube ; c, tentacles ; d, ovaries. 



throughout its whole length, but gradually 

 diminishing in thickness as they descend. 

 These filaments are equivalent to the ovigerous 

 tubes of the other Anthozoa ; but the ova are 

 here developed upon their external surface, to 

 which they are attached by short pedicles. 



Extending between the roots of the tenta- 

 cula of the polype and the margin of the tube 

 is the membrane, which, in the retracted state 

 of the animal, is drawn into the shape of a 

 funnel, the mouth of the funnel being con- 

 tinuous with the extremity of the calcareous 

 tube. The funnel-shaped membrane is in fact 

 a continuation of the calcareous tube, from 

 which it only differs in texture from the cir- 

 cumstance that the latter has become solidi- 

 fied by the interstitial deposition of calcareous 

 matter in its substance, while the former still 

 retains its softness and irritability. 



The funnel-shaped membrane does not ter- 

 minate suddenly upon the calcareous tube ; 

 the latter, indeed, is a prolongation and pro- 

 duct of it ; the calcareous substance is depo- 

 sited in this gelatinous membrane in the same 

 manner as phosphate of lime is deposited in 

 the bones of very young subjects, changing 

 its soft texture into hard and solid substance. 

 The manner, therefore, in which this tube 

 is formed cannot be compared to the mode 

 of formation of the cells of Serpulae or 

 the tubes of Mollusca ; in the latter it is a 

 secretion of the skin, almost an epidermic 

 product. In polyparies, on the contrary, there 

 is a real change of soft into solid substance, 

 which is effected gradually, but the calcareous 

 matter is not deposited in layers. 



. 



