BIOLOGICAL INVESTIGATIONS. 139 



series of faunas which preceded the known Paleozoic, and in 

 which the earliest known fossil faunas were slowly brought 

 into being. The objections to this hypothesis are, not only 

 that evolution probably proceeded with greater rapidity at first, 

 and that in every period the first coming in of types was sud- 

 den and in accordance with the law of phylogenesis stated 

 above, but, what is still more convincing, the researches of 

 explorers do not sustain this position. The great thickness 

 of unaltered rocks found in the lowest Paleozoic of the Colorado 

 Canon, and hunted over step by step by C. D. Walcott, whose 

 capacity for finding fossils in the field has perhaps never been 

 surpassed, and the researches of C. F. Matthews, an equally 

 careful field worker, in the Cambrian of Nova Scotia, and Wal- 

 cott again in Newfoundland, as well as all other observers in 

 other lands, have failed in discovering any confirmations of the 

 supposed former existence of preliminary faunas of the extent 

 required by Poulton's theory. If Darwinians had not only 

 looked upon animals theoretically as genetic series, but put 

 their views into practice and worked out examples of phylo- 

 genesis, they would long since have ceased to regard the uni- 

 formitarian hypothesis as tenable. 



The disregard of such researches will, I venture to suggest, 

 be found to affect all work upon the histology and embryology 

 of living animals. This must be the result if the theoretical 

 position taken in this paper be true, or even true in so far as 

 the nature of series is concerned. If series, for example, have 

 not been elaborated by uniform law, but by a process that is 

 forever changing its rate, and tending, as in the case of highly 

 retrogressive forms, like man, to depart so widely from the 

 parent type as to make their connections very difficult to 

 determine, it follows that all inferences with regard to phy- 

 logeny not based upon the comparative study of genetic series 

 are more or less likely to lead to erroneous conclusions. 



Perhaps the only researches in the embryology of existing 

 animals that may be said to have been followed out in accord- 

 ance with this view are those that have described the serial 

 relations of cells in the ontogeny and have refrained from draw- 

 ing phylogenetic conclusions, except perhaps the most general, 



