776 



THE NATURE BOOK 



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X(i. 3 {Sertularia ahieiina) 

 shows that variety which has 

 appropriated to itself "Sea 

 Fir " as its common name. 

 It is one of those most com- 

 monly found on the beach, 

 and also one in which the fir- 

 like growth is very distinctly 

 seen. It is quite a stiff struc- 

 ture, and of a hght fawn colour. 



The photos here reproduced 

 were obtained by the specimen 

 being placed on a piece of plain 

 glass in a printing frame, and a 

 sheet of photographic paper 

 being placed over it. The 

 frame was then exposed in full 

 sunshine until the part of the 

 ]mper where there was no " fir " 

 became almost black. The 

 prints were finished by first 

 washing for five minutes in a 

 solution of common salt (i oz. 

 of salt to 10 oz. of water), then 

 rinsing in clear water and fix- 

 ing in h\T30 bath (h^/po i oz., 

 water 7 oz.) for ten minutes. 



"SEA HAIR." 



catching microscopic atoms of food 

 with its fine tentacles. The colony 

 grows and grows, until there may be 

 many thousands of cells all forming 

 but one framework. 



These colonies may, as suggested 

 above, be found adhering to many 

 different objects — e.g. shells, seaweed, 

 and rocks : but the shell of a S])ider 

 crab is the finest buikhng site, for the 

 constant movement of the crab takes 

 the colony into fresh areas in which 

 to " fish " for food. 



Of the three illustrations. No. i 

 {Sertularia argentea) is commonly 

 called "Squirrel's Tail." and the 

 illustration shows how justified is the 

 name. This " fir " is of a much finer 

 form than some others, the cells being 

 much smaller. No. 2 {Sertularia oper- 

 ciiluta). commonly called " Sea Hair," 

 is extremely delicate, and has no cen- 

 tral rib as the two other kinds have. 



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"SEA fir; 



