LARVA OF ANNELIDS. 171 
been studied, the eggs are probably laid in masses between 
tide-marks, and the young, when hatched, swim freely on 
the surface of the sea. The eggs of other worms are carried 
about in lateral pouches. The germ undergoes a cleavage 
phase and a gastrula stage. We have observed, in Salem 
harbor, the development of Polydora (probably P. ciliatum 
Clap.) which may be found in August, in all stages, on the 
Fig. 117.—A, earliest observed stage of Polydora; B, Cephalula stage; Cand D, 
later stages.— Author del. B ydora; B, Cep age ; , 
surface of the water. When first observed (Fig. 117, A) the 
body was spherical, with a short, broad intestine, and two 
sets of large locomotive bristles. It then passed into the 
cephalula state, the head clearly indicated and forming a 
large hood. This stage is seen at B, which represents the 
under side of the cephalula, the mouth being situated be- 
tween the two large ciliated flaps (like the velum of larval 
mollusks) of the hood; the body is now segmented, with a 
third set of bristles and a band of cilia on the penultimate 
segment; afterwards as at C, dorsal view, additional rings 
are present ; the eyes are distinguishable, and there are two 
more sets of bristles. The new segments are, as usual in all 
