EPIPLANKTON 995 



have attached to them sedentary animals as well as other species 

 of algae. Among the animals, hydroids and bryozoans are the most 

 common, though other sedentary animals, such as Spirorbis, are 

 frequently abundant. Animals belonging to the vagrant type of 

 the benthos are by no means rare. The large fronds of the Lami- 

 naria cast up on our northern shores during every storm are fre- 

 quently veritable menageries of invertebrate life, which, under 

 favorable conditions, may float about for days. These fronds, for 

 example, are commonly covered with a dense growth of the delicate 

 littoral hydroids Obelia and Campanularia, while Bugula and other 

 Bryozoa and Spirorbis are usually common. The hollow stem is 

 commonly surrounded by an extensive growth of Membranipora, 

 while not infrequently tubularian and other hydroids find this a 

 suitable resting place. The root-like base of the stem often em- 

 braces the shell of Modiola or Cyprina, which in turn is over- 

 grown with coralline alg?e. Sponges are also found among the 

 "roots" of the Laminaria, and Acm^ea, Chiton, Crepidula, Anomia, 

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

 frequently takes its place. Finally, worms and crustaceans are not 

 rare 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, may be driven ashore. 

 Not infrequently they are carried far up into the estuaries and, 

 becoming stranded, are buried in the mud ; or else they are cast up 

 on mud flats behind some sheltering bar or ledge. 



While these cases illustrate an epiplanktonic existence due to 

 accident, the cirriped Lepas illustrates a habitually epiplanktonic 

 existence ; this barnacle rarely occurring except attached to floating 

 objects. Many of the animals found on the Sargassum seem to 

 be characteristic of it in its floating condition, not occurring on it in 

 its native haunts. (Ortmann-7.) Walther has adduced evidence 

 which goes to show conclusively that many of the larger fossil 

 Pentacrini, and perhaps other crinoids, occurred with their stems 

 w^ound around floating timbers, and he explains the occurrence of 

 these marine animals in fresh water coal strata as due to stranding 

 in estuaries of species leading an epiplanktonic existence. 



The marine or haloplankton forms one of the chief sources of 

 food for many marine animals and is everywhere devoured in 

 vast quantities. Dead organisms which sink to the sea-floor in an 

 incomplete state of decomposition form the chief element of the 

 organic oozes which furnish food to many littoral as well as abyssal 



