Chapter IX.— VARIATIONS IN STRUCTURE, 
Deformities in the adult stages of the higher Crustacea ceuter chietly in the large 
claws, which are more subject to mutilation than any other parts, owing to their 
constant use as weapons. We will therefore consider first the variations in these 
appendages. 
NORMAL VARIATIONS IN THE LARGE CLAWS. 
Aristotle ( 4 ) says of the claws of the lobster: u In the Astaci alone it is a matter 
of chance which claw is the larger, and this is in either sex.” The difference between 
the right and left claws is greatest in the small fiddler-crabs where, as in Gelasimus, 
the large claw, according to Bate, can not reach the mouth, a power which it must 
have originally possessed. 
It seems, as Aristotle remarked, a matter of chance whether the crushing-claw is 
on the right or left side of the body; but this is not really the case. I have shown 
that in Alpheus saulcyi , where the large crushing-chela can be recognized even before 
the animal is hatched, the members of a brood are either right-handed or left-handed, 
that is, have the crushing-claw on the same side of the body. This seems to be a case 
of direct inheritance from the parents, though not enough data were collected to settle 
this point. (For a statement of the facts, so far as they are known, see 94, p. 376.) 
The large claw occurs about as frequently upon the right side of the body as upon 
the left, without distinction of sex, as shown by the following table, embracing 2,433 
individuals : 
Sex. 
Crushing 
claw on 
right side. 
Crushing 
claw on 
left side. 
Both claws 
similar. 
Males 
562 
628 
1 
Females 
602 
638 
2 
Total 
1, 164 
1,266 
3 
ABNORMAL VARIATIONS IN THE CLAWS. 
SIMILAR CLAWS DEVELOPED ON BOTH SIDES OF THE BODY. 
A variation sometimes occurs in which the normal differentiation of the great 
claws is wanting. Both claws are similar, developed either for cutting or crushing. 1 
In examining over 2,400 lobsters, only 3 were found in which this abnormal variation 
was present. It is, therefore, undoubtedly rare, and apparently has never been 
previously described. Before examining these cases in detail it will be best to notice 
the normal characteristics of the claws. This description is taken from a female — 
length, 11 inches; weight, 24 ounces — with hard shell (compare fig. 20a, plate 15): 
Crushing -claw : On right side; seven marginal spines on propodus, third spine 
(from peripheral end) depressed; a small spine opposite the latter on upper side of 
propodus. There is a small tubercle on the upper side of propodus, near articulation of 
dactyl; in a corresponding situation below there are two tubercles, one considerably 
1 I have heard of a single case reported hy a fisherman, where similar crushing-claws were 
developed on both sides of the body. 
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