224 
Reviews — Nicholson' s Life-Hisionj of the JEarth. 
Under the “Biological Belations of Fossils” we are told that 
fossils “ have relations of the most complicated and weighty character 
with the numerous problems connected with the study of living 
beings, or, in other words, with the Science of Biology.” To such an 
extent is this the case that no adequate comprehension of Zoology 
and Botany, in their modern form, is so much as possible without 
some acquaintance with the types of animals and plants which have 
passed away.” 
Passing to the section of the work devoted to Historical Paleeon- 
tology, there are a few points to which the attention of our readers 
is particularly directed. At the end of eacb chapter, representing a 
geological period, Prof. Nicholson has introduced a list of the more 
important and accessible works and memoirs bearing on the period, 
or its fossils, treated of, under the general heading “ Literature.” 
This feature has already been carried out by some German writers, 
notablyby Carus and Gerstaecker in their “Handbuch der Zoologie,” 
and its adoption by Prof. Nicholson will, we think, be of much 
assistance to the Student, and add greatly to the value of the work. 
The stratigraphical sub-divisions of each period, irrespective of 
description, are well shown in the form of woodcuts representing 
vertical “generalized sections,” demonstrating the order of suc- 
cession of the various groups of strata, in one or other, aud 
sometimes several of the countries in which the rocks comprising 
the period are best developed. Supplementary to tliese “general- 
ized sections” are occasionally given “tabular views,” in which 
are shown the equivalent sub-divisions of a formation in various 
countries, ranged in parallel columns. We can only notice with 
brevity a few of the more strictly important palseontological facts 
brought forward by the autlior. The reasons for supposing the 
existence of an abundance of life during the Laurentian period are 
clearly brought forward. Wliilst speaking of Eozoon, the author 
considers “ that the balance of evidence up to this moment inclines 
decisively to this view ” (i.e. as to its organic nature). As a line of 
demarcation between the Cambrian and Silurian formations, Dr. 
Nicholson takes the Tremadoc slates, as proposed by Dr. Hicks. 
The structure of the Graptolites is entered into at some length, 
as might be expected from the author’s well-known acquaintance 
with this family ; he regards them as an ancient and peculiar group 
of Hydroida, and does not accept the Polyzoal affinities advocated by 
some writers. With regard to the advent of Vertebrates, we are 
rerainded that the curious bodies from the Lower Silurian rocks of 
Russia, termed Conodonts by Pander, may yet prove to be the teeth 
of fislies, recent researehes of Prof. Newberry liaving a tendency to 
establish Pander’s original conclusion as correct. We regard Prof. 
Nicholson’s remarks on the Devonian question with keen interest. 
With the view that the “Devonian formation has in nature no 
actual existence,” advocated by some authorities, he does not concur, 
but considers that its flora and fauna, as a wliole, are quite distinct 
both from the Silurian and Carboniferous. “This conclusion may be 
regarded as sufficiently proved even by the phenomena of the 
