THE REPRODUCTION OF THE SPECIES. 39 
mentary limb straightens out, and, though very small, 
acquires all the organization’ appropriate to that limb. 
At every moult it grows; but, it is only after a long time 
that it acquires nearly the size of its uninjured and older 
fellow. Hence, it not unfrequently happens, that crayfish 
are found with pincers and other limbs, which, though 
alike useful and anatomically complete, are very unequal 
in size. 
Injuries inflicted while the crayfish are soft after 
moulting, are apt to produce abnormal growths of the 
part affected; and these may be perpetuated, and give 
rise to various monstrosities, in the pincers and in other 
parts of the body. 
In the reproduction of their kind by means of eggs the 
co-operation of the males with the females is necessary. 
On the basal joint of the hindermost pair of legs of the male 
a small aperture is to be seen (fig. 3, A; vd). In these, the 
ducts of the apparatus in which the fecundating substance 
is formed terminate. The fecundating material itself is a 
thickish fluid, which sets into a white solid after extru- 
sion. ‘Che male deposits this substance on the thorax 
of the female, between the bases of the hindermost pairs 
of thoracic limbs. 
The eggs formed in the ovary are conducted to apertures, 
which are situated gn the bases of the last pair of ambula- 
tory legs but two, that is, in the hinder of the two pair 
which are provided with chelate extremities (fig. 3, B; od). 
