156 



CIDAKITES. 



M. Sars states, "In examining Echinus sphsera, I found 

 upon it all the three sorts of Pedicellaria described by 

 Muller, viz. P. tridens, P. triphylla, and P. globifera. 

 Besides what Muller states in regard to P. tridens, I will 

 make the following remarks : — Internally there is a hard 

 stem, which is enclosed by a strong transparent skin, like 

 a sheath. It is thickest at the upper and lower ends, and 

 reaches from the neck, as it is called, to the base, where 

 it remarkably enough is fixed and jointed to an exceeding- 

 ly small barb projecting from the Sea-Urchin's shell. 

 This circumstance, which is invariable in the Pedicellaria, 

 seems not to have been sufficiently attended to. The 

 three teeth are concave on the side turned inwards, 

 angular and furnished with small teeth on their edges. 

 They are hard and calcareous ; when viewed through a 

 microscope they are seen connected with very small glo- 

 bules arranged in rows. The stem is also calcareous, yet 

 it can be slightly bent without breaking. The neck is 

 nearly as thick again as the stem, it is fleshy, transparent, 

 and very flexible. The motions observed in the Pedicel- 

 laria when irritated, are, that the teeth close and squeeze 

 pretty firmly ; in this way by inserting the point of a pin 

 between them, after the Pedicellaria was torn off, I could 

 draw it out of the water ; further, that the neck bends and 

 inclines to all sides, and can even contract a little, in doing 

 which transverse wrinkles are formed on it ; and lastly 

 that the stem itself inflexible may bend along with the 

 whole Pedicellaria, to the side. The form called Pedicel- 

 laria globifera by Muller, has a head consisting of three 

 outspread flaps, standing nearly horizontally. Each of 

 these flaps is oval, very convex externally, and concave 

 internally, and at the upper end slightly indented and 

 provided with a sharp point somewhat bent. From the 



