1 62 WHAT MAY BE LEARNED FROM EOZOON 



original. In these the general form and habit of life are the 

 most likely things to change, the minute structures much less 

 so. We need not, therefore, be surprised to find its descend- 

 ants diminishing in size or altering in general form, while the 

 characters of the fine tubulation and of the canal system would 

 remain. We need not wonder if any sessile Foraminifer of the 

 Nummuline group should prove to be a descendant of Eozoon. 

 It would be less likely that a Sponge or a Foraminifer of the 

 Rotaline type should originate from it. If one could only 

 secure a succession of deep-sea limestones with Foraminifers 

 extending all the way from the Laurentian to the present time, 

 I can imagine nothing more interesting than to compare the 

 whole series, with the view of ascertaining the limits of descent 

 with variation, and the points where new forms are introduced. 

 We have not yet such a series, but it may be obtained ; and as 

 these creatures are eminently cosmopolitan, occurring over 

 vastly wide areas of sea bottom, and are very variable, they 

 would afford a better test of theories of derivation than any 

 that can be obtained from the more locally distributed and 

 less variable animals of higher grade. I was much struck with 

 this recently, in examining a series of Foraminifera from 

 the Cretaceous of Manitoba, and comparing them with the 

 varietal forms of the same species in the interior of Nebraska, 

 500 miles to the south, and with those of the English chalk and 

 of the modern seas. In all these different times and places we 

 had the same species. In all they existed under so many 

 varietal forms passing into each other, that in former times 

 every species had been multiplied by naturalists into several. 

 Yet, in all, the identical varietal forms were repeated with the 

 most minute markings the same. Here were at once constancy 

 the most remarkable, and variations the most extensive. If we 

 dwell on the one to the exclusion of the other, we reach only 

 one-sided conclusions, imperfect and unsatisfactory. By taking 

 both into connection we can alone realize the full significance 



