VIII. 



AT A SEA-SIDE LABORATORY. 



STUDENTS of the geographical distribution of animals find that the 

 key-word to their department of science is temperature. That is to 

 say, the most important of all those combined circumstances of food, alti- 

 tude, soil, etc., which affect the localization of a species, or cause a fauna 

 to be made up as we find it in any particular district, is the matter of av- 

 erage heat and cold. This is particularly true of marine organisms, which, 

 in a general way, are not only less active in winter than in summer, but 

 far more abundant near the surface — both in variety of kinds and in num- 

 ber of individuals — than at chilly depths, and in warm waters than in 

 northern and colder seas. The Gulf Stream, therefore, forms a very 

 important factor in estimating the distribution of the animal life of the 

 ocean, since its warm current permits many a southern form to wander 

 far to the northward in its genial track; just as, conversely, a range of 

 high mountains, such' as the Rockies, enables many a snow-loving animal 

 to creep almost to tropical limits along the lofty ridges, defying by the 

 aid of cold altitudes the arbitrary limits which latitude used to set to the 

 "zones" of organic life that were supposed to encircle the globe. 



There is thus found to be a startling difference in the oceanic fauna 

 north and south of Cape Cod ; the bather who has tried the surf at Na- 

 hant and then at Newport needs no thermometer to understand the im- 

 mense contrast of temperature between the two coasts. The reason is 

 plain : into Massachusetts Bay pours the icy flood from Labrador and the 

 berg-hannted banks of Newfoundland, while the south shore is washed by 

 the great tepid current from the tropics, which the Cape swerves off un- 

 til it strikes straight out to sea to warm the Irish coast. North of Cape 

 Cod, one picks up on the beaches, and dredges from the bottom of the 

 bay, few sea-animals (at least of invertebrates) except those of arctic habit, 

 and these grow more abundant as he proceeds northward ; while he misses 

 dozens and dozens of species that he knows may be collected merely by 

 crossing the narrow peninsula which has stood for ages, in some shape, a 



