POLYZOA 



905 



surrounded by a circle of tubular tentacles, which are clothed by 

 vibratile cilia; these tentacles, in the species we are considering, 

 \;ir\ from ten to twelve in number, but in some other instances they 

 are more numerous. l'>\ 

 the ciliary investment 

 of the tentacles the 

 Polyzoa are at once dis- 

 tinguishable from those 

 hydroid polypes to 

 which they bear a 

 superficial resemblance . 

 and with which they 

 were at one time con- 

 founded ; and accord- 

 ingly, while still ranked 

 among zoophytes, they 

 w c- 1 -e character] se< 1 as 

 r'lliitbraehiate. The ten- 

 tacula, are seated upon 

 an annular disc, which 

 i> termed the 1<>/>I><> 

 /ilnn-e, and which forms 

 the roof of the visceral 

 or perigastric cavity ; 

 and this cavity extends 

 itself into the interior of 

 the tentacula, 1 through 

 perforations in the lo- 

 phophore, as is shown at 

 I), fig. 687, representing 

 a portion of the ten- 

 tacular 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 lopho- 

 phore, as shown at A, 

 leads to a funnel-shaped 

 cavity or pharynx, 6, 

 which is separated from 

 the oesophagus, d, by a 

 valve at c ; and this oeso- 

 phagus opens into the 



\flftt 



FIG. 687. Structure of Laguncitla repens (Van Bene- 

 den). A, polypide expanded ; B, polypide retracted; 

 C, another view of the same, with the visceral 

 apparatus in outline, that the manner in which it 

 is doubled on itself, with the tentacular crown and 

 muscular system, may be more distinctly seen: 

 a a, tentacula ; 6, pharynx ; r, pharyngeal valve ; 

 d, oesophagus ; e, stomach ; /", its pyloric orifice ; 

 g, cilia on its inner surface ; h, biliary follicles lodged 

 in its wall ; i , intestine ; k, particles of excremen- 

 titious matter ; I, anal orifice ; m, testis ; n, ovary ; 

 o, ova lying loose in the perivisceral cavity ; p, out- 

 let for their discharge ; q, spermatozoa in the peri- 

 visceral cavity ; r, s, t, u, v, w, x, muscles. D, por- 

 tion of the lophophore more enlarged : a a, tenta- 

 cula ; b 6, their internal canals ; c, their muscles ; 

 d, lophophore ; e, its retractor muscles. 



stomach, e, which occu- 

 pies a considerable part of the visceral cavity. (In the Bowerbankia 



1 This communication between the tentacular and visceral cavities is denied by 

 Dr. Vigelius, who has recently made a careful search for it. 



