ch. ix.] SPECIAL-CREATION, OR DERIVATION! 451 



fishes, if such mollusk-like creatures as the amphioxus can 

 strictly be included among fishes; but presently here too the 

 lines begin to diverge, and we encounter reptiles and birds 

 on the one hand, and mammals on the other, all three being 

 related to fishes through the remarkable structures of living 

 and extinct batrachia. 



Such, as stated with crude brevity, is the classification of 

 animals most in accordance with our present knowledge. 

 Now from first to last, the farther we trace any one line of 

 development, the more widely we find it diverging from other 

 lines which originated in the same point. The higher insects 

 and crustaceans are not at all like worms ; but the myriapoda, 

 the lower crustaceans, and the caterpillars of higher insects, 

 are like worms. Viewed at the upper ends of the scale, the 

 mollusks are widely different from the vertebrates : viewed 

 at the lower end, the difference almost vanishes — the 

 amphioxus being closely similar in structure to the ascidians, 

 whose embryos present rudiments of a vertebral column. No 

 two animals could well be more strikingly unlike than a 

 wren and an elephant ; yet the lowest known mammal, the 



known vertebrate. Of all the "missing links," the assumed absence of 

 which is so persistently cited by the adherents of the dogma of fixity of 

 species, the most important one would here appear to have been found ; for it 

 is a link which connects the complex and hignly-evolved vertebrate with a 

 very lowly form which passes its natural existence rooted plant-like to the 

 soil, or rather to the sea-bottom. The ascidian cannot, indeed, be regarded 

 is typifying the direct ancestors of the vertebra ta. It is a curiously aberrant 

 and degraded form, and its own progenitors had doubtless once "seen better 

 lays." In its embryonic state it possesses a well-marked vertebral column, 

 and it behaves iu general very much as if it were going to grow to something 

 like the amphioxus. But it afterwards falls considerably short of this mark. 

 Already in early life its vertebrae begin to become " rudimentary" or evanes- 

 cent ; and when fully matured, it stops swimming about after its prey, and, 

 striking root in the sub-marine soil, remains thereafter standing, with its 

 broad pitcher-like mouth ever in readiness to suck down such organisms 

 floating by as may serve for its nutriment. That vertebrae should be found in 

 the embryo of such an animal is a most interesting and striking fact. It 

 rould seem to mark the ascidian as a retrograded offshoot of those primitive 

 wins on the way toward assuming the vertebrate structure, of which the 

 more fortunate ones succeeded in leaving as their representative the ani- 

 t )hioxo& 



G G 2 



