JOTTINGS FROM MY NOTE-BOOK. 217 



cealment similar to that furnished by a coat of 

 sea- weed. Old individuals of Hyas araneus, and 

 some of its allies, are often so loaded with Balaui 

 and Serpuhv on their head, body, and legs, that their 

 movements must be greatly impeded. In this state 

 their eyes are frequently so built up with these 

 organisms that only a small loophole is left to see 

 through, yet these sight-openings are seldom closed 

 up altogether. A question is here suggested : Does 

 the crab maintain the openings for the eyes, or does 

 the Serpula respect the wants of the crab? 



In deep water, where the bottom consists of soft 

 mud. this crab in most cases is free from parasitic 

 adornment. Although under other circumstances it 

 seems to encourage such vestments, the cause here 

 may be that as the colour of the crab is so much 

 like that of the mud, the resemblance affords a 

 sufficient means of protection. 



Many others of the crab family, inhabiting different 

 parts of the sea-bottom, are altogether free from 

 any such mask or false clothing. Among such are 

 the Poi'tunidcv. with whose swift- swimming habits 

 so great an encumbrance would be incompatible. 

 On the other hand, while so slow-moving a recluse 

 as the common Cancer pagurus, Lin., could not feel 

 much inconvenience from a little load on his back, 

 on most occasions he enjoys the immunity of bearing 

 a clean coat. It would therefore appear that these 

 associations depend as much on the condition or 

 peculiarity of the crab as on the choice of the parasite. 

 The young Hyas araneus, up to about lh inch in 

 length, looks as if covered with a natural growth, 

 but on closer examination this is found to be made 

 up of small bits of sea-weed closely packed together. 

 In others further advanced in size, the plants are 

 larger and have a more ragged appearance, and 

 sometimes grains of sand are thickly agglutinated 

 to the carapace. The adult is often so covered with 

 alga?, sponges, hydrozoa, &c, as to have a most 

 grotesque appearance ; but on the weedy bottom its 

 presence must be difficult to detect. 



