578 STRUCTURE OF POLYZOA : LAGUNCULA. 



tinguishable from those Hydraform Polypes to which they bear a 

 superficial resemblance, and with which they were at one time 

 confounded ; and accordingly, whilst still ranked among the 

 Zoophytes, they were characterized as Ciliobrachiata. The ten- 

 tacula are seated upon an annular disk, which is termed the 

 Lophophore, and which forms the roof of the visceral or perigastric 

 cavity ; and this cavity extends itself into the interior of the 

 tentacula, through perforations in the Lophophore, as is shown 

 at D, Plate xxn., representing a portion of the tentacular circle on 

 a larger scale, a a being the tentacula, b b their internal canals, 

 c the muscles of the tentacula, d the lophophore, and e its retractile 

 muscles. The Mouth, situated in the centre of the lophophore, as 

 shown at A, leads to a funnel-shaped cavity or Pharynx, b, which 

 is separated from the (Esophagus, d, by a valve at c ; and this 

 oesophagus opens into the Stomach, e, which occupies a consider- 

 able part of the visceral cavity. (In the Boiverbankia, and some 

 other Polyzoa, a muscular stomach or Gizzard "or the trituration 

 of the food intervenes between the oesophagus and the true diges- 

 tive stomach.) The walls of the Stomach, k, have considerable 

 thickness ; and they are beset with minute follicles, which seem 

 to have the character of a rudimentary Liver. This, however, is 

 more obvious in some other members of the group. The stomach 

 is lined, especially at its upper part, with vibratile cilia, as seen 

 at c, g ; and by the action of these the food is kept in a state of 

 constant agitation during the digestive process. From the upper 

 part of the stomach, which is (as it were) doubled upon itself, the 

 Intestine i opens, by a pyloric orifice, /, which is furnished with 

 a regular valve ; within the intestine are seen at Jc particles of 

 excrementitious matter, which are discharged by the Anal orifice 

 at I. No Circulating apparatus here exists ; but the liquid which 

 fills the cavity that surrounds the viscera contains the nutritive 

 matter which has been prepared by the digestive operation, and 

 which has transuded through the walls of the alimentary canal ; 

 a few corpuscles of irregular size are seen to float in it. The 

 visceral sacs of the different Polypides put forth from the same 

 stem, appear to communicate with each other. No other Respira- 

 tory organs exist than the Tentacula ; into whose cavity the nutri- 

 tive fluid is probably sent from the perivisceral cavity, for aeration 

 by the current of water that is continually flowing over them. 



447. The production of Gemmce or Buds may take place either 

 from the bodies of the Polypides themselves, which is what always 

 happens when the cells are in mutual apposition; or from the con- 

 necting stem or Stolon where the cells are distinct one from the 

 other, as in Laguncula. In the latter case there is first seen a 

 bud-like protuberance of the horny external integument, into 

 which the soft membranous lining prolongs itself ; the cavity thus 

 formed, however, is not to become (as in Hydra and its allies) the 

 stomach of the new Zooid; but it constitutes the chamber sur- 

 rounding the digestive viscera, which organs have their origin in a 



