79 



sideration, and we are free to say we have Dot found any embry- 

 ological, larval, mature or declining stages of development. Nor 

 has our study caused us to believe any one has or ever will find 

 such stages represented in the tests of the fossils under consid- 

 eration. 



If evolution has been the course of animal life, it must have 

 been commensurate with the lapse of geological ages, not only as 

 repr*sented by the deposits, but including the time indicated by 

 the unconformability and breaks that form the dividing lines be- 

 tween groups of rocks. And the interruption of the course found 

 at these dividing lines is far greater than the development or evo- 

 lution found within the deposits themselves. We are not sur- 

 prised, therefore, to find Saccocrinus and Cylicocrinus without 

 progenitors or descendants. They may have emigrated or been 

 driven by ocean currents from the homes of their ancestors to where 

 we find the tests; and in like manner they may have been carried 

 away to foreign climes not suited to their habits of life, where 

 they became extinct without leaving any degenerate descendants. 

 If such were the case, we will never see any but such natural 

 forms as we have found. Of course the smaller specimens may 

 have died younger than the larger ones did, but there is nothing 

 embryological or larval in their state of development. The largest 

 species are found, in the Niagara Group, at Chicago, Illinois, 

 the smallest species in Indiana, and the medium sized species in 

 New York; but all of them occur in the middle or upper part of 

 the Group, and they were not, therefore, ushered in at the be- 

 ginning of that geological age. 



What we have said of those two genera is also applicable to 

 Megistocrinus, that appeared at the outset, in the middle Devonian 

 rocks of Indiana and Michigan, with numerous species, varying in 

 size, from the smallest to the largest and with the greatest varie- 

 ties of form and structure, and then disappeared from the last 

 half cf the Devonian age, and crossed the vast lapse of time in- 

 dicated by the break, between the Devonian and Subcarboniferous 

 rocks, and reappeared, in the Chouteau Group, represented by 

 other and different species and again reappeared by other and dif- 

 ferent species in the Burlington Group, and then disappeared for- 

 ever. But there are no embryological or larval forms, nor any- 

 thing in the test of the last living species to indicate a declining 

 structure or degenerate descendant from the Devonian series. And 



