700 DEPTHS OF THE OCEAN 



the open ocean are found from 750 to 1000 metres, ascend 

 not only to the coast banks of Ireland, where the water is warm 

 and the specific gravity low, but also to the coast banks of 

 Newfoundland (see Fig. 489, p. 659, showing the vertical dis- 

 tribution of Clione on our northern track). 



How is this remarkable distribution to be explained ? 

 First of all it shows that our conclusions as to the distribu- 

 tion of animals must be drawn with great caution. Except the 

 single occurrence of Clione to the west of Ireland, all the 

 captures agree as to temperature, specific gravity, and viscosity, 

 both in deep water as well as on the Newfoundland banks. 

 We require further information regarding the physical and 

 biological conditions in order to understand the difference 

 between the coast banks and the ocean. The biological con- 

 ditions, especially the great difference between the food supply 

 on the coast banks and in the ocean, will be discussed after 

 touching upon certain physical conditions. 



As previously mentioned, Ostwald has pointed out the 

 influence exercised by salinity on the size of organisms ; in 

 surroundings of low salinity certain organisms absorb water and 

 increase in volume, while in high salinities they diminish in 

 volume. To what degree this fact may entail a difference 

 between the size of organisms belonging to the salt oceanic 

 waters and the size of organisms in the fresher coast waters, can 

 only be decided by future investigations. Possibly the richer 

 nourishment offered by coast waters affords the organisms a 

 better chance to store up fatty substances {^Clione as well as 

 Noctilitca store up fat), which increase the power of floating. 

 Finally, we may raise a question which seems to be worthy of 

 future investigation. Is the viscosity of the water influenced 

 by the number of organisms suspended in it } That this 

 may be so is conceivable when we think of china ink, for 

 instance, which is more or less viscous according to the amount 

 of substance dissolved in the water. Investigations as to the 

 actual facts occurring in nature have not yet been made. 

 Those who have observed the extent to which coast water 

 may be filled with suspended substances, detritus as well as 

 living organisms, may perhaps find this question worth con- 

 sideration. 



Migrations 



We have considered how far and in what manner the 

 appearance, shape, size, and also the several organs of different 



