1 86 NATURAL SCIENCE. march. 



Palaeozoic, Mesozoic, and Tertiary ocean in south-western Eurasia,, 

 but admit also great recent changes in the middle or southern Atlantic. 

 Geological evidence, therefore, does not prove, nor even point to, a 

 permanence of the great depths, at least in the oceansof the Atlantic 



type- 

 Let me remark in a few words that, although I believe in the- 

 possibility of the formation of large new depressions, I do not hold 

 with the old opinion, lately taken up again by M. Faye, that the con- 

 tinued sinking of the ocean beds may force chains of mountains tO' 

 appear all round. This view could only be propounded for the 

 Pacific basin ; but the Pacific chains are folded in the direction 

 toii'ards the ocean, and not /ww the ocean. They are easily divided 

 into arches, each of which presents the convex side to the ocean, so 

 that the Pacific everywhere presents the character of a " vorland." 



Let me, at the end of this long note, allude to a broad biological 

 fact. In the higher beings we see lungs always preceded by gills ; 

 so it is even with the human child. The adaptation for breathing our 

 atmosphere is of a later date ; and we conclude that the whole terres- 

 trial air-breathing fauna is a derived fauna, derived from amphibious- 

 forms quitting shallow water. This fact evidently points to a long 

 existence of dry land, long enough to permit this accommodation to 

 be effected ; the accommodation clearly has been going on since 

 Palaeozoic times. Still there exists no proof that individual continents 

 always remained the same, and we even know for certain that 

 such was not the case with by far the greater part of these 

 continents. 



A similar lesson is also taught by the eyes in all the higher 

 organised beings of the deep sea. The optical apparatus of abyssal 

 species is profoundly modified by the exceptional environment, while- 

 the normal types of eyes are met with in the same genera within 

 moderate depths. Therefore, we must also regard these deep-sea 

 forms as derived forms. The blind and blinded Trilobites of Cambrian 

 beds, the blind Trinuclei and the widely-expanded eyes in certain, 

 species of Aeglina in Lower Silurian strata teach the same lesson. 

 At the same time, they show that deep-water must have existed over 

 Bohemia, and over a good many other Palaeozoic tracts, and that the- 

 depths were considerable enough to call forth these same abyssal 

 metamorphoses of the eye. 



We might, therefore, rather be induced to infer that in Pre- 

 palaeozoic times there may have existed a universal hydrosphere or 

 panthalassa covering the whole of the planet. Only with the first 

 appearance of dry land began the deposition of clactic sediments.. 

 The higher forms of life may have been developed in waters- 

 of moderate depth and may successively have spread to the sun-lit 

 continents, and to the dark depths, while the slow elaboration of 

 the existing inequalities of the terrestrial surface was going on. 



But this elaboration is still in progress. I believe with Reyer^. 



