STAR-FISH AND SEA-URCHINS. 255 
position, and is called the madreporic tubercle 
(Fig. 32, m). Continuing our examination of the 
upper surface, we may observe, when we use a lens, 
a number of small pincer-like organs scattered about 
between the calcareous nodules, or attached to the 
spines ; these are known as the pedicellariz. Each 
Fig. 32. Upper surface of a Star-fish (Astropecten). (From Cassell’s “ Nat. 
Hist.”) 
consists of a stalk serving to support a pair of 
forceps or pincers, and the whole being provided 
with muscles, the stalk is able to sway about and 
the pincers to open and shut (Fig. 33). The entire 
mechanism is therefore clearly adapted to seizing 
and holding on to something ; but what it is that 
these curious organs are thus adapted to seize, and 
