sudden and general diffusion. Mr. Hyatt^ in his work of careful 

 analysis, describes and names 137 genera of tlie tetrabran- 

 chiates, all well marked by permanent transmissible and trans- 

 mitted differences. The greater number of these arose during 

 the very early period of the life of the globe. It is, of course, 

 conceivable that all these were the results of a natural law, 

 seated in the first and simplest specimen; nor, of course, would 

 this conclusion be at variance with the strictest theism. We 

 might believe that the curved form issued from the straight, 

 and the coiled-up creatures with fringed partitions grew out 

 of the simple ones with even septa; and, again, that the 

 forms uncoiled and ultimately again became straight as in the 

 bactrites of the chalk. But we have no instance whatever, in 

 the whole field of nature elsewhere, of any such series of 

 changes. Time works wonders, it is said, but does not work 

 wonders per se. 



On further inquiry into the relative numbers of the two 

 forms, taking the '^painful" labours of good Dr. Bigsby as 

 our guide, we learn that there are in the Silurian rocks 317 

 species of the extinct cyrtoceras, and 143 of orthoceras. In 

 the succeeding formation, the carboniferous, there are regis- 

 tered 24 of cyrtoceras and 114 of orthoceras.* 



We have thus the contemporaneous existence, through 

 untold ages, of these two typical forms of life, remarkably 

 alike, yet also actually different ; each species resembling the 

 other accurately, in all but the minute characters which sepa- 

 rated them ; each genus and species pursuing its own way 

 without change from age to age in the presence of countless 

 individuals of other genera and species living under precisely 

 similar conditions, yet the two families, the orthoceras and 

 cyrtoceras, ever remain distinct; no more changed by their 

 environments than Egyptian mummies in their grim com- 

 panionship, each enfolded in its own multitudinous wrappings. 

 As Professor Hall, of Albany (who has probably seen more of 

 these fossils than any one else), said to me last summer, " An 

 orthoceras was always an orthoceras and nothing else, and a 

 cyrtoceras was always a cyrtoceras and nothing else.^' 



I wish, therefore, to maintain that the one is not a variation 

 from the other, but a distinct thing, so far as we have actual 

 evidence ; indeed, modern geology is largely based on the 

 permanent or constant distinctions existing between organic 

 fossils. 



Prolonged experience has only strengthened the conclusion 

 drawn by William Smith, the father of English geology, 



* Bigsby's Thesa/urris ; Siluricus, 1860 ; Devonico-carboniferoiis, 1878. 



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