434 
WORMS. 
(Hermione hystrix), common in the Mediterranean, this coating of hairs is absent, 
and the scales are exposed, as shown in the accompanying illustration. In spite 
of their thick armature of spines, all the sea-mice are greedily devoured by fish 
of various kinds, such as 
cod, haddock, and dog¬ 
fish. Another well- 
marked family is that of 
the Nereides, in which 
the predatory character, 
coupled with ceaseless 
activity, rapidity, and 
sureness of movement 
reaches its highest ex- 
© 
pression. The head of the 
particular species {Nereis 
sea-mouse, Hermione hystrix (nat. size). incertci) lepresented in 
the illustration shows 
two pairs of feelers ( a and b), as well as several pairs of longer organs of the same 
nature (c), situated at the sides of the head. On the thrust-out and upturned 
proboscis may be noticed the two strong, sharp-toothed jaws (d) as well as several 
smaller horny teeth (e). In the worm named Heter¬ 
onereis, which is shown at A in the next illustration, 
one of the chief peculiarities is that the segments in the 
hinder half of the body are not so high as those in front, 
and that they are furnished with far longer bristles, 
whereas in Nereis all the segments are alike, being con¬ 
structed on the same plan as those of the front half 
of the body of Heteronereis. The exact nature of the 
connection between these two marine worms does not 
appear to be understood. The latter, however, seems to 
be a stage in the development of the former; but not 
an invariable stage, since adult examples of Nereis 
produce young sometimes like themselves, and some¬ 
times like Heteronereis. Allied to the Nereides is Palolo 
viridis, of the Samoa Islands. Of this species Stair and Powell write that “ every 
year the animal appears during October and November in countless numbers at 
different spots on the coast; but the second swarm is even greater than the 
first. . . . Both swarms seem to make their appearance on the day before the last 
quarter of the moon, and on this day, but especially on the day of the last quarter 
itself, the crowd of them is so inconceivably great that the sea, even far from the 
shore, seems to consist of nothing else. The worms appear with the dawn of 
light, and their number is at its height by sunrise, but after two or three hours all 
have vanished.” Curiously enough this mass of worms seems to be composed 
entirely of living fragments, entire examples being never met with. 
Two more types of roving predatory worms are shown in the same illustra¬ 
tion. Of these, Pliyllodoce Ictminosa of the French and English coasts has as many 
head of Nereis incerta 
(enlarged 4 times). 
