3 68 



ANIMAL LIFE-HISTORIES 



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st 



Fig. 890. Two just-hatched Crayfishes cling- 

 ing to Abdominal Appendage of their Mother, en- 

 larged, st, i, and o stalk, outer branch, and inner 

 branch of appendage; sh, empty egg-shells. 



groups that usually develop indirectly have either suppressed the 

 larval stage in their life-histories, or else made special provision 



for its safety. The former is what 

 has taken place in the Crayfish, in 

 which the large eggs hatch out into 

 little creatures that resemble their 

 parents in all essential particulars 

 (fig. 890). Nor do they at once 

 leave the mother, but for a time 

 attach themselves to the hardened 

 egg-glue which covers her abdominal 

 appendages, a safe means of attach- 

 ment being afforded by their pincers, 

 the ends of which are sharply hooked, 

 one of the few points of difference 

 from the adult. And it is said that 

 even when the young begin to swim 

 about on their own account, they at 

 first make but short excursions, from which they return to the 

 shelter of their mother's tail. 



Crustacean Dwellings. Omitting the 

 cases of those forms which obtain shelter 

 by association with other animals, as 

 these will be dealt with elsewhere, there 

 is little that need be said here. Many 

 Crustaceans live more or less in rock 

 crevices, at the openings of which they 

 lie in wait for prey. This is the case 

 with many Crabs, and the Rock- Lobster 

 (Palinurus) is distinguished by the same 

 habit. By turning over stones at low 

 tide one is pretty sure to find, in this 

 country a curious little Crab (Porcellana 

 platycheles) with hairy pincers, and also 

 species of the Sand- Hopper group. Sea- 

 Slaters shelter in rock crevices, and their 

 terrestrial brethren, the Wood- Lice, are 

 commonly to be found in the crannies 

 of masonry and also under stones. 



Some forms which burrow have already been mentioned 



nU 



ani.2 



Fig. 891. Alima Larva, enlarged. 

 ant. i and ant. 2, antennules and an- 

 tennae; i and n, first and second pair of 

 foot -jaws; vi-vm, last three thoracic 

 segments; ab., abdominal appendages. 



