The Comb Jellies and Others 71 



Although no season of the year is without its social 

 activities, it is on warm summer nights that these are at 

 their greatest height. During the dog days, the genial 

 temperature of the shore waters makes conditions par- 

 ticularly favorable for the growth of plant life; this 

 is reflected in the increasing abundance of animals, all 

 of whom are ultimately dependent on the vegetation of 

 the sea for sustenance. Moreover, the spawning of 

 most shore dwellers takes place at this time, and as a 

 consequence the water becomes extraordinarily popu- 

 lated. There is plenty to eat for all. 



And how well they know it! Making their way in 

 droves from the outlying reaches, the spider crabs 

 [Libinia emarginata) approach the shore or swarm 

 over the mussel banks, sometimes so thickly that the 

 bottom seems literally covered with them. They live 

 mostly on vegetable matter. These crabs are well 

 named; they look like giant spiders, with their flask- 

 shaped bodies and remarkably long, slender legs. The 

 males are the larger, and often have a spread of over 

 a foot and a half. Not only are these creatures the 

 largest of all the true crabs to be found along our 

 coasts, but another one of the spider crabs {Macro- 

 cheira kcinipferi), found in Japanese waters, is easily 

 the largest living crustacean of the world, measuring 

 fully twelve feet over all. However, the spider crabs 

 are less remarkable for their size than for the curious 

 habit they have of masking themselves with plants and 

 other growths. Sluggish and apparently stupid in their 

 ordinary habits, in this one instance they surpass all 

 other crustaceans in the display of reason : they will 

 purposely select certain seaweeds, hydroids, and other 



