92 KANSAS CITY REVIEW OF SCIENCE. 
which we believe we can prove, in the following pages, that this constant, ever 
present variation is always within a narrow limit. Thus, no two oysters, horses 
or menare just alike, but their varied appearance is within a narrow circle. No two 
members of the human family are just alike, yet we easily detect the German, 
French or Irish element, yea, even family traits, in the men we daily meet. This* 
constant variation, is accompanied by an equally constant adherence to the 
normal type. No two sharks are just alike, and different genera and species have 
a regular variance from each other, but the microscopic cell-form of the shark’s 
tooth, as given by Owen in his Odontography, is the same in the earliest tooth of 
the Devonian and in all later geological strata, as well as in the living sharks of 
our ocean. No two pine trees have the same shape, yet the cell-form of the 
wood, so small as to require a strong magnifier to see it, is always of the same 
elongated shape and with the same marking, whether from the Devonian age or 
from the living Auricarian pine. This unyielding persistence will be brought in 
view in the examination of the varied phases of organic life. 
In looking at the facts of geology the great rule is apparent that in a very 
general way the oldest fossiliferous strata contain only low types of animal and 
vegetable life, while the later formations contain higher forms, in proportion as 
they become more modern. This general rule, however fails in detail, as we 
shall endeavor to show. The oldest Silurian does not begin with the lowest 
forms of the five great sub-kingdoms of animals, as it should according to the 
laws of evolution, but has numerous representations of four sub-kingdoms, viz: 
Protozoans, Radiates, Mollusks and Articulates. The Protozoans, which are 
the lowest, and consequently according to the theory of evolution, should be the 
earliest and most abundant, are not found at the first; and when found are the 
least abundant of the Primoidal found. ‘The representatives of the Radiates, Mol- 
lusks and Articulates, are not the lowest of their kinds. This fact was thus 
strongly and clearly stated at a recent meeting of the British Association by Dr. 
Thomas Wright, President of Section C. ‘‘ Instead of a gradation upward in 
certain groups and classes of fossil animals, we find on the contrary, that their 
first representatives are not the lowest, but often highly organized types of the 
class to which they belong. This is well illustrated in the Corals, Crinoids, As- 
teride, Mollusca and Crustacez of the Silurian Age, and which make up the 
beginnings of life in the Palaeozoic period. The fishes of the Old Red Sandstone, 
we have already seen occupy a respectable position among the Pisces; and the 
Reptiles of the Trias are not the lowest form of their class, but highly organized 
Dinosauria.” 
Dana * also says, ‘‘If we may trust the records, Echinoderms, or the highest 
type of Radiates, were represented by species (Cystids and Crinids) long before 
the inferior type of Polyps existed.f” 
The examination of the Silurian fossils in detail are instructive on this point. 
Barande in his valuable publications on the Silurian, has given us the results of 
his studies on this system from twelve district regions. Dividing it into three 
Tee Nature, Aug. 2s, 1875, p. 307. + Mammal, p. 598. 
