158 CIDARITES. 



would certainly not always be the case if they were para- 

 sitical animals. Just as Lernsese are not always found in 

 all fishes, &c. 



" 2nd. The hard calcareous teeth or plates, and the in- 

 ternal stem also calcareous, and often filling up alone the 

 sheath, which are found in all Pedicellarise, bear a greater 

 resemblance to an Echinus spine than to any animal of the 

 Polype kind. There is neither opening, nor mouth, fila- 

 ments, &c. 



" 3rd. The Pedicellaria are firmly fixed in the skin 

 which envelopes the whole Sea-Urchin, upon a very small 

 projecting knob of the shell, to which knob they are 

 very strongly attached, but yet movable, like the prickles 

 of the Sea-Urchin ; the under surface of the stem of a 

 Pedicellaria being somewhat hollowed and articulated with 

 the knob. When a Pedicellaria is torn out, it is observed 

 that the sheath or skin connecting the stem is torn at the 

 lower end, which, doubtless, is a consequence of its connec- 

 tion with the skin, with which the shell of the Sea-Urchin 

 is covered, and which, when the Pedicellaria is torn out, 

 must be rent. 



" 4th. When the skin of the Sea-Urchin, or a single 

 Pedicellaria is irritated — for example, with a pin — the sur- 

 rounding Pedicellaria?, which stand in a wide circle, in- 

 variably bend themselves quickly towards the irritated 

 part. This phenomenon, which I have often observed, 

 shows clearly an organic connection between the Pedicel- 

 laria and the skin of the shell of the Sea-Urchin. The 

 same thing precisely is observed with the spines. 11 



On the purpose of these organs M. Sars remarks, " Per- 

 haps Nature, who has so abundantly provided the Sea- 

 Urchin with such an astonishing number of feet and 

 prickles, has also given the Pedicellarise as a sort of an- 



