BEHAVIOUR IN CONFINEMENT. 135 



The favourite haunts of these beautiful creatures are the 

 weed-covered rocks which are laid bare only at the lowest ebb of 

 the tide ; and in such situations one may occasionally find them 

 quietly at rest amongst the dripping alga?, or actively peram- 

 bulating the rock pools. Here, too, the explorer will often como 

 across the curious coils of spawn which they attach to the rocks, 

 and with which, when kept in confinement, they prettily bedeck 

 the sides of the Aquarium, where, by-the-way, it answers the 

 double purpose, first of ornament, and then of provender for tho 

 Nudibranch's companions in captivity. In most cases the spawn 

 is deposited in a loose coil of delicate gelatinous ribbon, standing 

 upright, and attached by its lower edge. But in some species the 

 ribbon form is substituted by a simple waved thread, one pretty 

 little fellow disposing this thread in tortuous undulations, like a 

 succession of figures of 8 ; while Doris pilosa, one of the " Sea- 

 lemous," and some others, deposit the spawn in the form of a 

 little cup or goblet, as delicate and beautiful as the most exquisite 

 of sea-nymphs could desire. 



In the Aquarium these animals are frequently observed to 

 mount the blocks of stone, or the glass sides of the vessel, and to 

 launch themselves out upon the surface of the water, where they 

 float bottom upwards, much after the fashion of the common 

 pond snails in our ditches and stagnant pools. Occasionally they 

 vary the performance, and let themselves down from the surface 

 by a delicate and almost invisible thread of mucus, and so 

 suspend themselves in midwater, as the caterpillars of the little 

 bell-moths are seen suspended from the oak-trees in the summer 

 sunshine. If disturbed, however, when suspended in this 

 manner, unlike the little caterpillars, which forthwith begin to 

 twist themselves about, taking in coil after coil of their silken 

 cables, until they have climbed up out of reach of danger, the 

 Nudibranchs at once let go their hold and sink to the bottom. 

 The whole of these delicate creatures appear indeed to be 

 extremely sensitive to external influences, and become agitated 

 and alarmed at the least suspicion of danger. 



this work are some of the most accurate and beautiful representations ot 

 living beings which have ever been produced ; and yet it is no disparage- 

 ment to say that even these illustrations convey but a very inadequate 

 idea of the transparent delicacy and beauty of the animals themselves. 



