INTRODUCTION. 



associate themselves with certain kinds of mollusk. Tlic 

 peculiarities of habitat arc very curious, and must be learnt 

 by observation and experience. 



The littoral Hydroids must be sought in the tide-pools, 

 both large and small, in the chinks and crannies of the 

 rock, on the underside of stones, and beneath the hanging 

 weed. I have described elsewhere (vide p. 298, note) the 

 method of search which is most likely to prove successful 

 in the case of the minuter species, and the apparatus 

 which is requisite. Of course a vast deal may be done in 

 a more "easiful" way; but the collector will find an ample 

 reward for his labour, whatever it may be, in the beauty 

 of the scenery which it will open to him, and the interest 

 of the material which he will gather. 



The larger Sertularian zoophytes, whose graceful plant- 

 like forms are so familiar, can only be obtained in the 

 living state by means of the dredge ; but the horny ske- 

 letons may be gathered on most sandy beaches, and fre- 

 quently in great profusion, after stormy winds. Large 

 tangled masses of them, which are full of beauty in them- 

 selves, are cast ashore, and if examined while still fresh 

 and moist will often be found to conceal some of the 

 smaller kinds in a living state. The dredge, indeed, is 

 essential to those who would thoroughly investigate the 

 Hydroida ; but rich material for study and a great variety 

 of forms may be obtained on the shore. 



The free medusiform zooids may be captured with a hand- 

 net from the rocks, or by means of a tow-net from a boat, 

 especially in still, warm autumn weather, when they swarm 

 near the surface of the sea. They are difficult to keep ; 

 and few have as yet succeeded in obtaining and hatching 

 the ova, and tracing the development into the polypite 



d 



