NATURAL, HISTORY OF AMERICAN LOBSTER. 
333 
and often successful capture of copepods and other members of the plankton or floating 
population, showing that they can direct their movements with a certain degree of 
precision when necessary or when the light and other conditions are favorable. 
The body of the little lobster is armed at most vulnerable points with defensive 
spines, and its various appendages bristle with tactile hairs or setae, as well as with 
more diminutive spines, which may afford some slight degree of protection against 
smaller enemies when they do not assist 
it in seizing and tearing its prey. 
The free margin of the “paddle,” 
or forked telson plate, as commonly 
seen in the larvae of the higher Crus- 
tacea, is garnished with very uniform 
and symmetrical spines and plumose 
hairs. 
It is interesting to observe that cer- 
tain spines and the setae whatever their 
size or function, from the rostrum or 
tips of the claws down to the smallest 
microscopic hair, agree in their essen- 
tial structure, and are all developed as 
tubular folds or outgrowths of the 
integument. In the course of the pre- 
natal molt all the spines as well as the 
hairs are telescoped or invaginated. 
(Compare p. 269-270.) 
In swimming the young lobsters 
use the outer branches or exopodites 
of the thoracic limbs (segments ix-xiv, 
table 4), by the beating movements of 
which they are slowly driven upward, 
downward, or forward (compare fig. 40), 
and the abdomen, by the sudden fold- 
ing of which and by the aid of its broad 
telson plate, they dart rapidly back- 
ward. Each thoracic leg, in conformity 
to the type of decapod limbs, consists 
of a short stalk or protopodite and two diverging branches, the outer branch or exopodite 
which serves as a flexible “oar,” being flattened and fringed with long feather-like hairs. 
The “oars” work independently of the inner branches, which in the larva are 
mainly prehensile organs, and which with the stalk alone give rise to the adult limbs. 
The concerted vibratory strokes of these minute flexible oars is so rapid and so uniform 
in vigorous larvae that at a short distance from the eye it is impossible to follow their 
movements. 
1 
Fig. 37, 38, and 39. — Parts of setae from cheliped of larval lobster, 
showing different degrees of reduction from typical plumose 
type. Enlarged 85 times. 
