102 New York State Museum 



of frost and cold. Sand Hoppers along the beach have 

 been found burrowing for several inches into these 

 masses of seaweed which in the process of decomposi- 

 tion produce great heat. 



Effects of variability in salinity. Variation in sa- 

 linity of the sea water, especially if it is abrupt, has a 

 disastrous effect. The normal salt composition of sea 

 water permits the development of a fauna rich in spe- 

 cies and genera. If there is a reduction in the salt con- 

 tent of the water the result is an impoverished fauna, 

 that is, a fauna poor in species, poor in lime and 

 dwarfed in size, though often rich in individuals. 

 Marine animals have been divided into three groups 

 according to their ability to live in water of various 

 degrees of salinity: (1) types (stenohaline) that can not 

 live in water with less than 30 or 35 parts per thou- 

 sand of salt (normal open sea) ; (2) types (enryhaline) 

 that can endure without injury a considerable freshen- 

 ing of the water — they need the salt but not a definite 

 percentage, and will live as long as any salt remains; 

 (3) types (brackish-zvater) that are adapted to a small 

 amount of salt and an increase of the salt is just as 

 harmful as a reduction. The brackish state of water 

 has not been exactly defined but the upper limit is two 

 or three parts per thousand of salt. The types of the first 

 division outnumber those of the other two in all groups 

 of animals. Fresh water is poisonous to the majority 

 of marine animals. The whole cmestion is one of the 

 degree to which the living tissues of the animals can 

 be permeated by solutions of varying composition and 

 density. It has been found that the salt content of 

 the blood of the Shore Crab (Carcimts moenas) varies 



