54 THE WALKS ABROAD OF 



transparent moss, something like agglomerated soap- 

 bubbles. 



" Sacculina," said Le*on; "a singular parasite of 

 the crab, and one that has for a long time defied the 

 perspicacity of the learned. Indeed, it was only last 

 year that its exact history was discovered." 



" Something new, and yet true ! Let me hear it." 



" With pleasure. The Sacculina, whose entire body 

 is not represented by this moss that you see, com- 

 mences by being a microscopic crustacean, a Cypris, 

 who comes quietly, and as if meaning no ill, and fixes 

 itself by one antenna to the still tender hind-body of 

 the quite young crab." 



" Capital ! And what next ? " 



" Then it undergoes a change. As the habitation 

 seems to suit it, and it has no desire to seek its fortune 

 elsewhere, it establishes itself in this position, casts 

 off its legs, no longer of any use to it, and replaces 

 them by a hollow needle of peculiar structure. And 

 it is by the aid of this organ, which is a perforator, 

 though itself pliable, that the heretofore Cypris, turn- 

 ing its outside inside, like a glove or stocking, glides 

 gradually into the interior of the crab. 



" After this it can give up active life and live like 

 a lord. It finds in the interior of its host both bed 

 and breakfast, and this new arrangement suits it so well 

 that you may almost see it waxing fat. This it does 

 so thoroughly that its apartment soon becomes too 



