THE CRUSTACEA 157 



and become a casing in which its owner can face the dangers 

 of the open world once more. 



This Ecdysis presents many interesting points. Not 

 only is the external and visible portion shell of back, tail, 

 legs, antennae-, and eyes cast off, but with this, and all 

 without severance, the internal shelly parts as well. The 

 covering of the gills, the complicated honeycomblike 

 structure termed the " Endophragmal System," the lining 

 of the stomach, with its internal " teeth " and the blade- 

 like processes which act as tendons in each joint all are 

 cast, and in the same position as they occupied in life. This 

 is a puzzle in animal mechanics too long to explain here, 

 but which a little thought will show is not so very difficult 

 to unravel, bearing in mind, as a clue, that the internal parts 

 are, as it were, inward folds of the outside. 



One more curious feature in Ecdysis. If a crab has, some 

 time prior to the process, lost a leg or two, an eye or claw, 

 the emerging form has these in perfection. (This quite 

 independent of the frequent process of the replacement of 

 lost limbs from a bud which appears on the scar.) If a 

 limb gets broken off just before the moult I do not know 

 what happens. This I have not seen, and in this book 

 I am nowhere quoting, only telling of what I have 

 observed. 



Let us get back to the shore crab (Carcinus mcenas). We 

 have seen him a Zoea, then a Megalope, now he has as- 

 sumed the form of his parents, and is living at the sea- 

 bottom. 



This species abounds on all our shores, living from high- 

 water mark to nearly, but not quite, the lowest zone 

 that is, it is strictly a " littoral " species. 



The adult male is about two and a half inches across 

 the back. Its colour is usually olive-green ; in some 

 localities it is bright green ; in others brownish red, but 

 shades of green are the most frequent. A line of white 



