Page:The Scientific Monthly vol. 3.djvu/514

 5o8 TEE SCIENTIFIC MONTHLY

Ever <:liuigii]g dkaraeter-fomi and character- f auction,

Ever clianging character-veloeitr in individiial derelopment and

the fthromatin, Erer changing character- cooperation, coordination and cornlatioD, In eo Mant character-origin in the chromatin, aometimee following,

■ometimee antecedent to character-origin in the organiam, BelatiTelj rapid diaappearance of character-form and -function in

the indiTidiial, Belativel^ alow diaappearance of character- form and -function in

the chromatin. J

FORK SVOLUTION OF TUS TEIITEBBATES DNDXR THE UBCKANICAL Ain)

PHYSICO-CHEUICAL ACTIONS, BEACTIONS AND INTEBACTIONS OV

LOCOICOTION, OFFSNSE AND DEFENSE, AND BBPBODUCTIOH*

OrdoviciaD time, the early Paleozoic epoch next above the Cam- brian, is the period of the first known vertebrates, the fossil remains of fish dermal defenses found near Canon City, Colorado, as announced hy Walcott in 1891, and subsequently in the region of the present Big Horn Mountains of Wyoming and the Black Hills of South Dakota. Small spines referred to Acanthodian sharks are also abundant in the Ordovician of Canon City, Colorado. Since they were slow-moving types protected with the beginnings of s dorsal armature composed of small calcareous tubercles, to which the group name Ostraeoderm re- fers, probably these earliest known pro-fishes were not primitive in external form but followed upon a long antecedent stage of vertebrate evolution. In the fonn-evolution of the vertebrates relatively swift-

��Fia. T, Tn Ekistino L*ncb

be llttarnl lone the sole survl

Iter Wllley.

movini;, defenseless types are invariably antecedent to slow-moving, armored tv'pes.

Ancestral to these Ordovician vertebrates were free-swimming, > For the geologic history the author is chieflj indebted to hii fellow acad- emician, Cliarlea Scbuchert. For the luteal knowledge regarding the evolution of the vertebrates to hia Columbia Univereitj colleague, William K. Oregorj.

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