MIRACLES OF SCIENCE 



gill or atrial chamber, and the structure of the dermal 

 skeleton were intermediate in character. But the 

 most important features of all were the long-sought- 

 for mouth parts or jaws. They were paired, consist- 

 ing of four separate jaws, which in chewing or biting 

 moved to and from a median line, like the jaws of 

 all known arthropods. They were not unpaired 

 arches moving forward and backward as tney had in 

 all true vertebrates." 



The character of the mouth, then, allies the ostra- 

 coderm to the tribe of spiders and scorpions rather 

 than to the vertebrates. But it chances that studies 

 of the embryos of vertebrates, say of a frog, show 

 that at its earlier stages of development each indi- 

 vidual vertebrate passes through a stage in which 

 its jaws have the character of the jaws of the ostra- 

 coderm. Inasmuch as it is an accepted thesis of bi- 

 ology that the embryo of a higher organism repro- 

 duces in epitome the history of racial evolution, this 

 seems clearly to imply that the developing verte- 

 brates in point of fact passed through a stage in 

 which their mouths were like the mouth of the ostra- 

 coderm. 



There are many other points of the embryological 

 story which are equally suggestive, but which have 

 explicit meaning only for the trained anatomist. 

 Suffice it that Professor Patten is convinced that the 

 facts of embryology go hand in hand with his studies 

 of the fossils in giving support to his theory of the 

 arachnid origin of the vertebrates. Needless to say, 

 the theory will not be accepted without controversy. 

 But pending further investigation, we are justified 



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