10 Bulletin Wisconsin Natural History Society [Vol. 11, Nos. 1-2 
At the time the observations were made, the season was not 
far advanced and the temperature was still somewhat cool — -the 
ocean was once as low as 6.5° C.; the air varied from 11.8° C. to 
24.2° C. Detailed observations were made at fourteen different 
stations, the locations of which are shown in figure 1. 
II. THE ROCK BEACHES 
The rock beaches are subdivided into horizontal zones each 
of which is dominated by characteristic animals or plants. At 
most stations five such zones were readily recognisable: (1) the 
rocks and pools above the limits of high tide, (2) a zone popu- 
lated almost entirely by Balanus, (3) Ascophyllum and Balanus , 
(4) Fucus, (5) Chondrus. The stratification at Nahant is more 
complete and differs somewhat in its characteristics from that 
described by King and Russell (’09) at Millport on the coast of 
Scotland. The zones will now be considered in order, beginning 
with the highest. 
