262 THE HORSE FOOT CRAB. 
between this rim, and the perimeter of the anterior shield. 
To the unaided eye this rent is altogether imperceptible, but 
opens on the exertions of the animal; and at this opening it 
emerges from the old shell. Now as the opening is at the 
front, and in the place of the greatest width, and moreover 
as the shell is sub-coriaceous, and somewhat yielding, and 
at this particular place is very thin, it may be seen how great 
advantage the animal has in this matter over the higher crus- 
taceans whose moult, from necessity, takes place from behind, 
and whose shell is composed of a more unyielding material. 
Iu the exuviation of Limulus I fancy a close likeness to that 
of the insects when leaving the pupa. The King Crab 
emerges at the forward, but under side of the cephalic cov- 
ering ; the beetle at the forward, but dorsal side of the same. 
It is plain that Limulus has an easier time in getting off his 
old coat than his “more respectable relations" have. To see 
the King Crab, as it were, coming out of himself, is a sight 
so odd as to draw from those beholding it the exclamation 
“it is spewing itself out of its mouth.” 
When the animal, specially noticed above, had come out 
of its old shell it was nine and a half inches in the shorter 
diameter of the cephalic shield ; while the vacated shell was 
but eight inches by the same measurement. If they moult 
more than once in the year this would make their growth 
quite rapid; and if they do not, it seems to me that they 
must attain an age of not less than eight years before reach- 
ing the size that indicates adult life. But we must speak of 
this farther on. I have observed that every spring, that is, 
so soon as the water has lost its winter temperature, large 
numbers of the young of the previous summer are found in 
the shallows. These range from dn inch to two and a half 
inches in the shorter diameter. As the ereature when begin- 
ning life for itself, is but a scant quarter of an inch in diam- 
eter, this would imply rapid growth, and I think that the 
larger of the above have probably lived through two winters. 
There are reasons for believing that the spawn is deposited 
