DIVERSITY OF LIFE 153 



below the sea-level, sloping almost imperceptibly towards 

 the south-west, and having a temperature all the year 

 round of 35° Fahr. Scattered here and there our 

 dredge finds waterworn pebbles of pumice-stone, which 

 have sunk after having in all probability been carried 

 thousands of miles by ocean currents before they became 

 water-logged and fell to rest. 



Pitch-dark and freezing cold as this part of the 

 submarine plain is, we discovered nearly fifty species of 

 animals which must actually live upon it, not including 

 some free-swimming species that flit in the canopy of 

 water above it, and probably pay it only occasional 

 visits. If we inquire into the inter-relations of these 

 fifty species we shall discover a striking illustration of 

 the fact that, given a tract where the conditions are 

 uniform, then if life greatly flourishes upon it, it must 

 be diversified life ; for these fifty species, all practically 

 living on one plot of land, belong to thirty-six different 

 genera, twenty-four different families, eight different 

 classes, and five distinct phyla or subkingdoms." 

 Growing on its surface, like plants on a heath, there 

 are several kinds of Hexactinellida [Hyalonema, Holas- 

 CMs, Saccocalyx, Bathydorus), those beautiful glass- 

 sponges already spoken of as characteristic of the 

 deep sea ; and encrusting the roots of some of these, 

 barnacles of two kinds were found. Starfishes, sea- 

 cucumbers, and sea-urchins of over thirty different 

 kinds creep over these oozy pastures, many of them 



