44 



Animal Life by the Sea-shore. 



as i\legalopa, similar to a little crab, except for the abdomen, 

 which is carried extended. In this last condition the larva 

 swims actively for a little time, and then sinks to the bottom, 

 where, after one more moult, the perfect form is attained. 

 The crab is then about the size ol a lentil, and grows larger and 

 larger at each successive moult. 



The development of such a typical Brachjairous form suggests 

 that the crabs are derived from " long-tailed " ancestors, and, as 



a matter of fact, 

 forms filling the 

 gaps between the 

 two extremes 

 exist in Nature. 

 Such intermediate 

 types, which can- 

 not find a place 

 either among the 

 Macrura or among 

 the Brachyura, 

 are assigned to a 

 separate division, 

 Anomura (irregu- 

 lar tails), the 

 members of which 

 diit'er widely from 

 one another, some 

 being suggestive 

 of lobsters, others 

 of crabs ; yet all 

 agree in having 

 the abdomen 

 modified to some 

 extent, the essen- 

 tial characteristic 

 being the reduc- 

 tion in size of the 

 last pair of walking-legs. One very common representative of 

 this group, the Squat-Lobster {Galatliea squamijera), is often found 

 under stones at low tide (Fig. 46). It is about three inches 

 long, of a dark greenish brown colour, and has somewhat the 

 appearance of a little lobster, the carapace and abdomen being 

 almost equally de\'eloped, the latter ending in a fan-like tail. 

 Its position among the Anomura is indicated b}/ the ^'ery small 

 size of the last pair of legs and by the wa^' in which the abdomen 



V'<''''(T'f|iW 



riC. 46. SCALY GALATHE.\ (AI'TER BELL) 



