335 



bryozoante attached to the floating Sargassum and other 

 alga?, and the Crustacea, molluscs and other animals 

 living among their branches. 



A large number of alga?, especially the shallow-water 

 forms, have attached to them sedentarv animals us well as 

 other species of alga?. Among the animals hvdroids and bry- 

 ozoans are the most common, though other sedentary ani- 

 mals, such as Spirorbis, are frequently very abundant. Ani- 

 mals belonging to the vagrant type of the benthos are by no 

 means rare. The large fronds of the Laminaria, cast up on 

 our northern shores during every storm, are frequently veri- 

 table menageries of invertebrate life, — which under favorable 

 conditions may float about for days. These fronds, for ex- 

 ample, are commonly covered with a dense growth of the deli- 

 cate littoral hydroid Ohelia geniculate, while Bugula and 

 other Bryozoa, and Spirorbis are usually common. The hol- 

 low stem is commonly surrounded by an extensive growth of 

 Membranipora, while not infrequently tubularian and other 

 hvdroids find this a suitable resting place. The root-like 

 base of the stem not uncommonlv embraces a shell of 

 Modiola or Cyprina, which, in turn, is overgrown with coral- 

 line alga?. Sponges are also common among the "roots" 

 of the Laminaria, and Acmea, Chiton, Crepidula, Anomia, 

 and other molluscs are attached to the shell, or the stone, 

 which frequently takes its place. Finally, worms and crusta- 

 ceans are not uncommon inhabitants of the sheltering space 

 between the branches of the "roots"; and sea-anemones, 

 small star-fish, brittle stars, and sea-urchins also occur, 

 both on the basal portion of the stem and on the frond 

 itself. Such floating menageries may be carried far out to 

 sea, or, what is perhaps more frequent, they are driven on 

 shore. Not infrequently they are carried far up into estu- 

 aries, and, becoming stranded, are buried in the mud ; or 

 else they are thrown upon mud-flats, behind some shelter- 

 ing bar or ledge. 



While these cases illustrate a pseudo-planktonic existence 

 due to accident, the cirriped Lepas illustrates an habitually 



