EDWARD FORBES. 211 



zone,' extending from fifty fathoms to about one hundred 

 fathoms or more in depth. In this zone animal life is 

 much less abundant than in the preceding, and among the 

 more characteristic types in the northern seas, at any 

 rate are certain kinds of corals, which only live and 

 flourish in deep water. 



In his researches in the JEgean Sea, Forbes recognised 

 the occurrence of similar zones, but he thought they were 

 capable of further subdivision. He recognised in the 

 Eastern Mediterranean, in all, eight well-marked ' regions 

 of depth,' each of which is ' characterised by its peculiar 

 fauna, and when there are plants, by its flora.' The 

 lowest of these zones was beyond the limit of what he had 

 called the 'deep-sea coral zone,' and extended from a 

 hundred and five fathoms in depth to two hundred and 

 thirty fathoms, beyond which depth his explorations were 

 not carried. In this zone, animal life was extremely 

 sparse; the species were mostly small; and the shells 

 were mostly pale-coloured or white, in part, apparently, 

 owing to a deficient supply of light. As just remarked, 

 Forbes did not dredge at a depth of more than two 

 hundred and thirty fathoms, which at that time was 

 considered an extraordinary depth for the carrying out 

 of dredging operations. Owing to the great reduction 

 in the number of species of animals which he found at 

 this depth, he came to the conclusion that at depths 

 greater than this the animals would become fewer and 

 fewer, and that they would ultimately be found to dis- 

 appear altogether. In accordance with these observa- 

 tions, he placed the 'zero of animal life' at about 

 three hundred fathoms, and he concluded that at all 



