No, 381.] A HALF-CENTURY OF EVOLUTION. 653 
swamped, and we find no trace of them in the strata yet 
examined. 
Thus far, indeed, paleontology is silent! as to the mode of 
origin of the amphibian limb, as it is concerning the origin of 
arthropod limbs from the parapodfa of annelids. Unfortu- 
nately, and this is still a weak point in the evolution theory, 
nowhere do we find, unless we except the Archzopteryx, 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 showing distinct progressive steps in a 
change of function. Hence arises the very reasonable view 
held by some that nature may make leaps, and that new 
adaptations or organs may be suddenly produced. No inad- 
apted plant or animal as an entire organism has ever been 
observed either among fossils or existing species. Man has 
some seventy vestigial structures, but his body as a whole, not- 
withstanding the disadvantages of certain useless vestiges, is 
in adaptation to his physical and mental needs. 
While the true Carboniferous labyrinthodonts 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 spe- 
cialization had taken place. Forms like Peleon and Branchio- 
saurus had gills and four legs; others were like our lizards, as 
in Keraterpeton; 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 
1 Paleontology is also equally silent as to the origin of pleisosaurs and ichthyo- 
saurs from their terrestrial digitigrade forbears; though in Archaeopteryx we have 
an unusually suggestive combination of reptilian dnd avian features. Certain 
Theriodontia point with considerable certainty to the incoming of mammals such as 
the Echidna and duckbill, but as to the steps which led to the origin of brachio- 
pods, echinoderms, trilobites, of Sirenians and of whales, paleontology affords no 
indications. 
