46 



when I expressed the same belief in regard to the Vertebrata *, and defined it as " the 

 deep and pregnant principle in Philosophy " t evolved in the researches on the general 

 homologies and archetype of the Vertebrate Skeleton. 



The series of facts added to biology in the present centviry by these researches, with 

 other correlated series, palseontological and embryological, of the kinds illustrated in the 

 present memoir, render " thaumatogeny %", or the hypothesis of direct creation of species, 

 inadequate to their explanation. The invocation, by Cuvier, of successive miraculous 

 interventions, creative and destructive, to solve or explain the phenomena of the succes- 

 sion of extinct species, chiefly made known by his grand discoveries, recalls the com- 

 plexity of cycles and epicycles invoked to explain the facts of astronomy as they had 

 accumulated in the time of Copernicus. He knew not how the twofold movements of 

 the earth (rotation on its axis, revolution about the sun) were governed ; but the hypo- 

 thesis on those postulates simplified the comprehension and explanation of the pheno- 

 mena of the heavens. 



So the way of operation of " nomogeny," or the incoming of species by secondary cause, 

 remains to be demonstrated ; but its expository relation to the phenomena is a guarantee 

 of its truth. Volition, with exercise and disuse of parts, invoked by Lamarck, are of the 

 nature of " causae verse," but inadequate ; premature births, congenital departures from 

 parental characters, suggested by "Vestiges," meet some of the phenomena; "Natural 

 Selection " suggests other conditions of " nomogeny." 



Biology is in its Copernican stage. The analogy to Astronomy is close. The objection 

 to the Canon of Frauenberg, that the rate of the whirl required by his hypothesis would 

 send into space all things loose on the earth's surface, is akin to some of the cavils, as 

 seemingly fatal, to the evolutional view. The analogy of the course of physical science, 

 and the accelerated rate of progress of those of life, since DeMaiUet, Lamarck, and 

 Oken, ceased to be exceptional advocates of Nomogeny, justify the expectation that this 

 hypothesis will be developed into a known law, and one day receive its crowning demon- 

 stration from the Newton of Biology. 



§ 12. DESCKIPTION OF THE PLATES. 

 Plate I. 



Limulus polyphemus. 



Fig. 1. Alimentary canal, hepatic ducts, part of the liver, and of the muscular system, in situ, viewed 

 above, or from the dorsal aspect. 



A. Cephaletron : a" its postlateral spinous pro- i. Compound eye. 



duction ('genal spine' of Trilobitology) . a 1. Ocelli. 



B. Thoracetron. h. Entapophysial pit of hindmost (by auchy- 

 c. Baseofpleon. losis) cephaletral segment. 



* On the Nature of Limbs, 8vo, 1849, p. 86. t lb. p. 10. 



+ Anatomy of Vertebrates, vol. iii. p. 814. 



