ZOOPHYTES. 47 



to do more than indicate a few of them here, leaving the 

 reader to make wider acquaintance with a most interesting 

 group by studying the species in Hinck's British Marine 

 Polyzoa. 



The Sea-mat (Flustra foliaced) is a deep-water form, whose 

 colonies take the shape of fronds, resembling Fucus serratus 

 in outline ; but it is thrown up on the beach in great quantities, 

 and it will be one of the first things you will find on the shore, 

 especially if you rout about among the weeds washed up by 

 every tide. Creeping over these flat frond-like masses you 

 will probably find other species that take a more branching 

 form, such as the common Creeping Coralline (Scrupocel- 

 laria reptans), or the more bushy Bird's-head Coralline 

 (Bugiila amcularid). The Tufted Ivory Coralline (Crisea 

 eburned) has tubular chambers of ivory whiteness ; it is of 

 branching habit, and occurs on some of the red seaweeds. 

 The Foliaceous Coralline (Membranipora pilosd) runs in very 

 narrow ribbons, covered with a " pile " of bristles, up the 

 stems of various weeds ; and many another of the nearly two 

 hundred and fifty British species will be sure to fall to the 

 patient and sharp-eyed investigator. 



The horny cell in which the polypide resides is really its 

 own cuticle or outer skin, to which it is inseparably attached. 

 If careful examination be made, it will be found that at the 

 mouth of the so-called cell the horny material suddenly changes 

 its character and becomes a very fine and delicate tissue, 

 capable of the greatest freedom of movement and folding such 

 as is absolutely impossible with the horny portion. This 

 remarkable change of character in the two portions of the 

 same cuticle allows the anterior portion of the polypide, with 

 its crown of tentacles, to be suddenly and completely with- 

 drawn out of danger, just as easily as the tip of a glove-finger 

 can be withdrawn into its lower portion. 



The tentacles that encircle the mouth of the polypide are 

 hollow, and covered with ever-waving cilia, whose beating 



D 



