THE STARFISH AND CLOSELY RELATED ANIMALS. 147 
Characteristics of Echinodermata. This sub-king¬ 
dom enjoys the distinction of being the most exclusive 
division of the animal kingdom. These animals secrete 
bony plates in the skin; they have marked radiate 
structure, almost always being divided into five radiat¬ 
ing parts. With the radiate structure we may also 
trace a bilateral condition. (In the case of the starfish 
this condition may be seen by drawing a line through 
the madreporic body and the opposite ray.) The 
water-system with its ambulacral feet is peculiar to this 
sub-kingdom. All are marine. 
Topics for Reports. The Burrowing of Sea-urchins. 
Sea-cucumber as Food. Radiate Structure. Where I 
Have Seen Echinoderms. The Senses in a Starfish. 
Young Starfishes. Basket-fish. Stone-lilies. 
VOCABULARY 
Ab o'ral (Lat. ab , from, and os, 
mouth), the surface opposite the 
mouth. 
Am bu la'cral (Lat. ambulo , to 
walk about), a word applied to 
the walking areas of Echino¬ 
derms. 
Am pul'la, pi. ampulla (Lat. 
ampulla , a flask), the enlarged 
end of one of the tube-feet of 
an Echinoderm. 
De cal'ci fy (Lat. de, from, and 
calx , lime), to remove the calca¬ 
reous matter. 
Gen'i tal o pen mgs, the openings 
for the passage of eggs and sperm 
in starfishes and sea-urchins. 
Mad re por'ic body, a hard plate 
pierced with holes through 
which water filters into the tube- 
feet of a starfish or sea-urchin. 
O'ral (Lat. os, the mouth), pertain¬ 
ing to the mouth. 
Ped i cel la'ri a (Lat. pediculus , a 
small foot or stalk), a minute 
pincer-like organ on the skin of 
an Echinoderm. 
Ra'di ate (Lat. radius, a ray), 
having the parts regularly ar¬ 
ranged around a centre. 
