122 Prof. M'Intosh on the 



Mr. Wallace thinks that temperature and the depth of the 

 water are of primary importance in the distribution of the 

 marine fishes, for many species are adapted for shores and 

 shallows. Yet it is difficult to see how either acts ; for 

 example, some shore-fishes, like the five-bearded rockling, 

 have pelagic eggs and still more actively pelagic young, so 

 that the question is complex. It must be admitted, however, 

 that many peculiar fishes frequent the great abysses (the 

 temperature of which does not vary much). 



Is temperature sufficient to explain the varied distribution 

 of the vast variety of fishes? Does it make impassable 

 barriers, for instance, between the temperate and the tropical 

 and subtropical regions ? Such can hardly be the rule in 

 every case, since, as Mr. Boulenger has pointed out *, the 

 grey mullet (Mugil capita) ranges from Scandinavia to the 

 Cape, and is as much at home at the mouth of the Congo as 

 off' the shores of Northern Europe. Yet some, such as the 

 cod, prefer the colder northern waters, and range from the 

 shores of Norway to those of North America; whilst others, 

 like Cha'todon and the Sphyraenidae, choose the warmer 

 waters of tropical and subtropical regions. The variations 

 in temperature which a fish is capable of enduring are not, 

 perhaps, sufficiently known, but the northern plaice survives 

 in the warmer waters of Australia after a protracted journey 

 of thousands of miles. Prof. Prince f, moreover, in an inter- 

 esting article on "Adaptation in Fishes," mentions that 

 Prof. Jordan found in the volcanic geyser area of the Yellow- 

 stone Park suckers and chubs in water of 85°-88° F., and 

 young trout in a temperature about 75° F. It is long since 

 the eggs of the flounder were heated in a test-tube at St. An- 

 drews, and yet they survived and healthy larvae were hatched 

 from them. 



Moreover, in roughly grouping the fishes under Dr. Sclater's 

 six oceanic regions the families seem to be inextricably inter- 

 woven throughout, some occurring in every area or ranging 

 from the North Atlantic to the Indian Ocean, and thence to 

 the Pacific. A few features given by Mr. Wallace from 

 Dr. Giinther's work are noteworthy. Thus six families out 

 of about eighty are confined to the northern seas, and 

 amongst them are the suckers and the sturgeons. One family 

 (one genus and one species) is restricted to New Zealand 

 waters. Four inhabiting the depths of the ocean are only 

 found in the Atlantic, whilst thirteen families occur only in 



* Poiss Ben. Congo, p. 355. 



t ' The Ottawa Naturalist/ vol. xiv. no. 11, p. 216. 



