While the crab is young and rapidly growing, frequent exuviations take place at short intervals, from three to five times in the course of one year. Previous to the change, the animal almost ceases to feed, and becomes rather inactive; the proper time having at length arrived, exuviation is effected in the course of a few hours, body and limbs being alike relieved from their hard covering.
Another specimen kept was of smaller size, the opposite extremities of the limbs being only thirteen lines asunder; its colour was green, with three white patches on the back. In the course of little more than a year five exuviations took place at irregular intervals, the new shell and animal becoming larger each time.
In the middle of the nineteenth century, England alone, and with absolute conviction and determination, demonstrated to the civilised world the beneficial results in diminishing the death-rate of large towns, to be obtained by cleanliness, the destruction or removal from man's body and surroundings of organic "dirt," viz. his excreta, the exudations and exuviations of his body, the waste and fragments of his food.