288 



SCIENCE. 



[N. S. Vol. VIII. No. 192. 



may, however, be surmised that certain of 

 the lung-fishes or forms like them, adapted 

 for breathing the air direct when out of the 

 water in the dry season, instead of remain- 

 ing in their mud cells waiting for the rains 

 to fill the lakes or swell the rivers, at- 

 tempted, like the Anabas, or climbing fish, 

 to migrate in schools overland ; or, like that 

 fish, which is said to have become " so thor- 

 oughly a land animal that it is drowned if 

 immersed in water," it may have become 

 confined to the land, and, losing its gills, 

 used its lungs only. As a final result of its 

 efforts to walk over the damp soil and mud 

 of swampy regions the unaxial fins may 

 have developed, through the strains and 

 pressures of supporting the clumsy body, 

 into props with several leverage systems ; 

 the basalia, instead of remaining in one 

 plane as in a fish's fin, spreading out and 

 becoming digits to support the weight and 

 steady the body while walking. This pro- 

 cess was not confined to one or to a few 

 individuals, but, as Lamarck insists in the 

 cases he mentions, it affected all the indi- 

 viduals over a large area. Those indi- 

 viduals with incipient limbs became erased 

 or swamped, and we find no trace of them 

 in the strata yet examined. 



Thus far, indeed, Paleontology is silentf 

 as to the mode of origin of the amphibian 

 limb, as it is concerning the origin of arthro- 

 pod limbs from the parapodia of annelids. 

 Unfortunately, and this is still a weak point 

 in the evolution theory, nowhere do we find, 



■*Parkerand Haswell's Text-book of Zoology, Vol. 

 II., p. 220. 



t Paleontology is also equally silent as to the origin 

 of plesisosaurs and ichthyosaurs from their terrestrial 

 digitigrade forbears, though in Archijeopteryx we 

 have an unusually suggestive combination of reptilian 

 and avian features. Certain Theriodoutia point Tvith 

 considerable certainty to the incoming of mammals, 

 such as the Echidna and duckbill, but as to the steps 

 ■which led to the origin of the brachiopods, echino- 

 derms, trilobites, of Sirenians and of whales paleon- 

 tology affords no indications. 



unless we except the Archseopteryx, clear 

 examples of any intermediate forms between 

 one class and another ; each species as far 

 as its fossil remains indicate seems adapted 

 to its environment. 



There are numerous cases of vestigial 

 structures, but no rudimentary ones show- 

 ing distinct progressive steps in a change 

 of function. Hence arises the very reason- 

 able view held by some that nature may 

 make leaps, and that new adaptations or 

 organs maj^ be suddenly produced. No in- 

 adapted plant or animal as an entire organ- 

 ism has ever been observed either among 

 fossils or existing species. Man has some 

 seventy vestigial structures, but his body as 

 a whole, notwithstanding the disadvantages 

 of certain useless vestiges, is in adaptation 

 to his physical and mental needs. 



"While the true Carboniferous labyrin- 

 thodonts were few and generalized, with 

 gills and four legs ; already in the Permian,^ 

 where we meet with some thirty forms in. 

 the Ohio beds alone, and about as many in 

 Bohemia, a great modification and speciali- 

 zation had taken place. Forms like Peleon 

 and Branchiosaurus had gills and four legs; 

 others were like our lizards, as in Kera- 

 terpeton ; Dendrerpeton and Hylonomus of 

 Nova Scotia were more lizard-like and with 

 scales ; others perhaps swam by means of 

 paddles as in Archegosaurus; others, like the 

 ' Congo snake,' were snake-like with small 

 weak legs, as CEstocephalus ; some had gills 

 but no legs, as in Dolichosoma, while in 

 others the limbless body was snake-like 

 and scarcely larger than earth worms, as in 

 Phlegethontia of the Ohio and Ophiderpeton 

 of the Bohemian coal measures. 



Already, then, in Permian times the 

 stegocephalous type showed signs of long 

 occupation, old age and degeneration. The 

 process of degeneration and reduction in 

 and loss of limbs may have been initiated 

 as far back as the closing centuries of the 

 Devonian. 



