[fraser] HYDROIDS OF Till-. VANCOUVER ISLAND REGION 103 



Many of those although occasionally found at low tide are much 

 more commonly found in the water at various depths. By far the 

 commonest shore form in the neighborhood of the Station is Obelia 

 longissima, which grows on floats, piles, etc., in great masses. It is 

 present practically the whole year through and liberates medusa* 

 through an extended period. Gonothyrœa clarki is plentiful in spring 

 and early summer but later seems to die off. Syncoryne mirabilis is 

 common in spots and the medusae, commonly called Sarsia mirabilis, 

 are extremely plentiful in the early summer. After these are liberated 

 the hydroid dies off and nothing is seen of it later in the year. 



The majority of the others can scarcely be said to be common 

 above low tide mark along any shores visited. Rather the upper 

 limit of their bathy metrical range is near that mark and at very favor- 

 able tides, a few specimens may appear out of water or within reach 

 below the surface. Many that are not included in this list are found 

 in quite shallow water and it may be a matter of accident that some 

 of them have not been found at low tide as well. Practically all the 

 specimens have been got at a depth that may be considered slight in 

 comparison with the depth of the water farther out in the Strait of 

 Georgia or out some distance from the shore in the open ocean. 



The accompanying table will serve to give an idea of the relative 

 number of species that have been found in districts in the region, which 

 although convenient for enumeration, are of necessity somewhat 

 arbitrarily chosen. Naturally the east coast of Vancouver Island 

 and the San Juan Archipelago show the largest numbers as the greatest 

 amount of work has been done here, but from the little collecting that 

 has been done on the west coast of the island and the region to the 

 northward, they promise particularly well. Such localities as Swift- 

 sure Shoal on the west coast and Nawhitti Bar to the north of the 

 Island, as well as other points that might be mentioned, will doubtless 

 yield as great a variety as any similar areas that have been 

 investigated. 



As the occurrence of each species is written up as completely and 

 precisely as possible, it would be of no special value to go into detail 

 here concerning the relative abundance of the different species in the 

 various families. 



