488 
Analyses of Books. 
[August, 
beings slumber undisturbed and unconsciously throughout the 
dry, dusty summer days, awaiting, however, only the fall of the 
evening dew or passing shower, to cast off the frail cerements 
that enclose them, and to re-awake to aCtive sentient life. The 
concluding paragraph of this splendid chapter is so very sugges- 
tive, that no excuse is needed for its quotation : 
“ One final though indirect result of the rigid scrutiny to which 
the monads and other low unicellular organisms have been sub- 
m-tted, in order to solve the mystery of their generation, remains 
to be recorded. As conclusively proved by Professors Tyndall, 
Dallinger, and Drysdale, Cohn, Kuhne, and other investigators, 
such organisms in their germinal or sporular state can success- 
fully resist exposure to temperatures that prove fatal to any other 
more highly organised structures, even up to and beyond the 
boiling-point of water. So far, therefore, as they are brought in 
contadt with the ordinary conditions of the earth’s surface, they 
are practically indestructable. Nay, more ! as suggested by 
Prof. Tyndall, there is no reasonable pretext for assuming that 
there are not germs capable of resisting far higher temperatures 
than those which have been hitherto subjected to experiment. 
Hence, among all known organic forms, the infusoria and their 
allies alone would appear to possess the power of weathering the 
cataclysmic changes of the universe, and, secure from all influ- 
ences of heat and cold, of migrating in safety through inter- 
planetary space.” 
The sixth chapter on classification commences with an account 
of the first attempt at arrangement by O. F. Muller, in 1786. It 
is founded on the appearances presented by the limited optical 
appliances of the time, the leading distinction being the absence 
or possession of external organs. After deducting various 
Rotiferse, &c., and low vegetable organisms, about two hundred 
species of true Infusoria are described. 
Ehrenberg’s system depends mainly upon the supposed exist- 
ence of one or many digestive cavities, or their absence, the 
structure of the infusoria being supposed by this great observer 
to be far more complex than more recent observations have 
proved it to be, after eliminating as before, other forms, about 
three hundred and fifty species remain. These systems of classi- 
fication are given in full, as are those of Dujardin, Siebold, Perty, 
Claparede and Lachmann, and Diesing and Stein. 
The author’s investigations with high powers among some of 
the forms of Flagellata, and the discovery of some peculiarities 
about the oral region, have led to very great alterations in the 
system of classification adopted in the description of the various 
species. The three divisions which follow, containing a syste- 
matic description of the Infusoria, occupy by far the greater 
portion of the work, and beside the technical matter of the 
diagnosis, habitat, &c., gives as much information as can be 
obtained about each species, in very many cases embodying the 
author’s own observations. 
