156 THREE CRUISES OF THE " BLAKE." 



and more constant, or even in the deeper regions perfectly 

 uniform, sjDecies of the most varied derivations, when they had 

 once attained a certain zone, could spread everywhere. This 

 explains at once how the deejD-water fauna presents a very uni- 

 form composition in all regions of the globe, but at the same 

 time includes various species the analogues of which live in the 

 sublittoral regions of both cold and hot climates, and may have 

 sent an occasional wanderer into deeper waters. 



While the little dredging thus far done in deep water has 

 added to our knowledge a large number of antique types which 

 strongly remind us of tertiary, cretaceous, and even of Jurassic 

 forms, we should not forget that such antique types occur 

 everywhere, in limited numbers, it is true, both in the shallower 

 regions of the sea and in fresh water. We can only say that 

 in the deep-water fauna a relatively larger number of such 

 antique forms has been found than elsewhere. In contrasting 

 the littoral with the continental and the abyssal faunae, the 

 last shows a closer affinity to types of a former period than 

 does the fauna living at higher levels, where the descendants 

 of antique types are also met, but have become familiar from 

 their common occurrence. There are in deep waters no ga- 

 noids ; to-day their representatives are found iu the fresh waters 

 of Australia (Ceratodus) and of North America (Lepidosteus). 

 Neither are there any deep-sea graptolites or belemnites. 



Old-fashioned animals like Trigonia, Limulus, and Lingula are 

 all from shallow water, as are also Amphioxus and Cestracion. 

 No species of characteristic palaeozoic corals have been dredged, 

 and nothinof- resemblino" the remarkable crinoids, so abundant in 

 former times. The affinities of the deep-sea types recall to us 

 mesozoic and cainozoic types, such as we find in the chalk and 

 tertiaries. No such old-fashioned animals have been discovered 

 as throw new lioht on our zoolooical knowledg-e, althousfh, as 

 Moseley well says, in our deep-sea explorations we obtain for 

 the first time a glimpse of the fauna and flora of nearly three 

 quarters of the earth's surface. Our whole knowledge of the 

 sea bottom has been created within a few years ; before that 

 time we knew little of its fauna and flora bevond what is found 

 on a comparatively narrow belt of the coast line. 



