268 
BULLETIN OF THE BUREAU OF FISHERIES. 
When these claws are magnified thirty or forty times (fig. 15 and 16) the first steps 
in the differentiation of the crushing from the primitive toothed type of claw become 
evident. They are expressed by a blunting or rounding off of the sharp points of the 
teeth, and a tendency to fusion among those situated at the proximal extremity of both 
divisions of the claw. (Compare fig. 21-24.) 
We therefore conclude that during the fourth, fifth, and in some cases at least in 
the sixth or even seventh stages of the 
lobster, both of the big claws represent 
the older or phylogenetic type which is 
retained as the toothed or lock forceps of 
the adult. The chela destined to become 
the crusher is a little broader though 
not necessarily longer than its fellow, and 
its teeth which still show the periodic 
sequence are more rounded, as we have 
just seen, at the proximal end of the series. 
The tufts of sensory hairs are, moreover, 
less prominent on the future crushing 
claw, as apparent in all the later*stages. 
The development of the toothed type 
of claw is represented by a series of draw- 
ings (fig. 17-25, and pi. xlii) from the first to the ninth or tenth stages, in which the orderly 
appearance of the spines can be followed with approximate accuracy up to stage 3, and 
with certainty beyond it. The large propodus only is represented in most of the figures. 
The spines of the toothed claws are developed in a linear series, and the order in 
respect to size corresponds to that of age, or time of appearance. The larger teeth of 
the first order are the first to 
emerge. They are set at wide in- 
tervals and evenly spaced. From 
2 to 3 are recognized in the chelae 
of the first larva (fig. 17) and from 
3 to 5 in the claw of the second 
stage (fig. 18). In the third stage 
the normal number of primary 
teeth are present (fig. 1 9) , although 
some of them are very small, and 
in the intervals between them are 
interpolated rudiments of the teeth 
of the second order. In a single series the first trace of the third series of teeth may 
be detected also. At the fourth molt (fig. 20) a single period of eight may be com- 
pleted by the intercalation of the four small teeth of the fourth order; but the process does 
not always stop here, and an attempt, so to speak, is often made at the seventh, eighth, 
or at some subsequent molt to introduce a fifth series of 8 teeth, which if completely 
Fig. 18. — Outline of corresponding part of big claw shown in figure 17, but in 
second larval stage, showing the separated primary teeth, invaginated 
claw-tip, and setae, as well as a new spine arising at either end of the 
series. Spine 1 of period m now bears the duct of a gland. See figure n. 
Fig. 17. — Outline of great claw tip, showing serrate margin of pro" 
podus, in first larval stage of the lobster, represented as a trans- 
parent object, from glycerine preparation. Note the invagi 
nated sensory hairs or seta ( s ), and claw-tip ( t ^), and three 
teeth of the first order (1, 1, 1) developing from apex to base 
and representing the three primary periods (1, 11, m), indicated 
in figures n and 18; also a tegumental gland opening at the 
tip of each of the two oldest spines. 
