THE DECAPOD CKUSTACEA. 205 



sure the new shell being large enough to allow of sub- 

 sequent growth. Try to boil and eat a "soft" crab, and 

 you will speedily realise the condition of affairs. The 

 process of moulting in a large crab is to be counted as one 

 of the most impressive of the phenomena to be witnessed 

 on the shore, and may often be watched by a close observer. 

 During and after the moult the crab is absolutely helpless, 

 and until the shell grows hard again is at the mercy of 

 every foe. The crab realises clearly its 'helpless condition, 

 and always seeks shelter in some nook or cranny of the 

 rocks. Even there, however, it is not always safe, and is 

 attacked by members both of its own and other species, 

 who greatly appreciate the succulent morsel. Moulting is 

 in consequence a process full of risk and danger to all 

 Crustacea, but it is the price which has to be paid for the 

 advantage of a coat of armour. 



Moulting occurs in all Crustacea, and many times in the 

 life of each individual. The cast coats of the different 

 species are always abundant about the shore rocks, and are 

 often mistaken for dead crabs. They are always interesting 

 and worth study, and can be recommended to those who 

 have scruples about killing animals for dissection purposes. 



In still one other respect the Crustacea are of great 

 interest. This is in regard to their development, which is 

 markedly indirect, the young being usually very unlike the 

 adults. Examine a female Mysis, or opossum-shrimp (see 

 p. 209), with young in her brood pouch, and you will find 

 that the young are in most respects similar to the parents. 

 This is one of the exceptional cases where the development 

 is direct, and without distinct metamorphosis. It is other- 

 wise with the majority of the Crustacea. In the crabs, for 

 instance, the eggs are carried about by the mother only till 

 they hatch, and the larvae when hatched (see Fig. 92) are 

 very different from the mother. They are minute, trans- 

 parent creatures, colourless save for the eyes, with quaintly 

 shaped body furnished with long spines and few appendages. 

 Such embryos are called zoeas, and their relation to the 

 adult crab was for long unknown. The zoea stage of the 

 common shore crab is to be found in vast numbers on the 

 surface of the sea in autumn, but is more likely to be got 

 by tow-netting than in rock pools. The zoea grows and 



