204 



POPULAR SCIENCE MONTHLY 



evident, and in Figure 10 is shown an arrangement of algae and ani- 

 mals upon a much creviced slate. Barnacles of two distinct types and 

 mussels, mingled with a growth of Endocladia muricata, appear in this 





,^:^^r4ri^^^;'| 



Fig. 14. CORALLINACEAE AT THE EDGE OF A TlDE-POOI., ON THE RiGHT AMPHIROA AND ON 



THE Left Corai.lina. 



view, but the general grouping is less clearly concentric. Nevertheless 

 the Endocladia zone is pretty well defined as a mid-tide algal society 

 and sometimes shows sharp demarcation when favorably situated for a 

 pure growth. 



■■iv J-" -Jt ■ '• 



Fig. 15. A Plant of Codium -Mr( kunaii m < ai.ifukmi i'\i, a Cii AUArTKRi.sTif Siphonacaeous 



ai.(;a of the Tii)i;-Pooi.>>. 



Among the high-tide algae — those occupying the upper zones — Pel- 

 vetia is an interesting form. It occurs at the same levels adopted by 



