POLYPIFERA. 



23 



tentacles, as he considers that when fully ex- up like a fan. The observations of the same 

 tended the tentacle is by their action folded writer lead him to consider that there is no 



Fig. 26. 



Hydra fusca. {After Corda.) 



a, natural size ; b, magnified, extended ; c, magnified, contracted, viewed vertically, so 

 that the mouth is seen ; d, magnified, contracted ; e, foot. 



communication whatever between the interior 

 of the tentacula and the cavity of the bod}', 

 for the tentacle is filled up with the albuminous 

 material in which are dispersed brown co- 

 loured granules, apparently of an oily nature. 



In the wart-like nodosities which wind 

 in a spiral course round the tentacula, Corda 

 finds what he considers to be organs of touch 

 (Jig. 27, d, and fig. 28, 1, 2). Each of these 

 consists of a delicate sacculus implanted in 

 the wart-like excrescence (fig. 28, p), which 

 encloses another (q), provided with thicker 

 walls and containing in its interior a minute 

 cavity (r). Every one of the singular bodies 

 thus organized supports an almost impercep- 

 tible filament (s), completing the supposed 

 tactile apparatus. 



In the midst of every group of these 

 filament-supporting vesicles was found an 



instrument adapted to seize prey, which its 

 discoverer names a dart (hasta). This 

 apparatus consists of a transparent oval sac 

 (fig. 28, /), imbedded in the substance of the 

 tentacle (k), and furnished above with a small 

 orifice (h). At the bottom of the sac is 

 situated a saucer-shaped body (), upon which 

 is placed a solid oval corpuscle (11), and this 

 again supports a long and sharp spicnlum 

 (sagitta), composed of calcareous matter (o), 

 capable of protrusion and retraction through 

 the aperture k, apparently by the evcrsion 

 and retroversion of the saucer-shaped bladder 

 to which the oval basis of the dart, n (has- 

 tifi-r), is appended. Whenever the Hydra 

 would seize any animal, the darts of the 

 tentacle become extruded, and its whole sur- 

 face is thus rendered tenacious. Yet this 

 does not seem to be all ; it would appear that 



c 4 



