CRABS, ETC. 81 
of the abdomen (Fig. 85), and are carried about by the 
mother. When first hatched they are generally in the 
zoza stage. The eyes of the zowa (Fig. 
87, @) are large and black. From the 
carapace extends upward a long horn, an- 
other projecting downward like a tusk. 
They moult several times, gradually chang- 
ing to the megalops form (Fig. 87, 4), and 
finally, after successive moults, seek the Fis. 86.—A few 
bottom and assume the adult shape (Fig. See 
87, c). enlarged. 
Order I. Barnacles (Cirripoda).—The 
barnacles are fixed crustaceans, and partly from this cir- 
cumstance were long considered mollusks. The adult 
Fic, 87.—Metamorphosis of the crab (Carcinus manas). A, zoma stage; 
&, megalops stage ; C, ready to seek the bottom. 
Balanus (Fig. 88) is round, with a broad base, and at- 
‘taches itself to shells or rocks, The newly hatched young 
are free-swimmers (Fig. 89, 4), but soon acquire a bivalve 
shell, B, and attach themselves to the bottom by their 
