62 
POPULAR SCIENCE REVIEW. 
A second chapter treats of the sub-kingdom Protozoa, and the position 
to be assigned in its ranks to the Infusoria. Our author accepts the 
sub-kingdom Protozoa in the old, that is to say, the pre-Hackelian sense, in- 
cluding the Sponges, and altogether rejecting the ‘ kingdom ’ Protista. He 
defines the group i as embracing all those forms of life referable to the 
lowest grade of the animal kingdom, whose members are for the most part 
represented by organisms possessing the histologic value only of a single 
cell, or of a congeries or colonial aggregation of similar independent uni- 
cellular beings.’ His views of the classification of the Protozoa appear at 
first sight a little complicated, inasmuch as some of his primary sections 
overlap one another in the classes, or at least in the class Flagellata, which 
includes representatives of three primary sections, so that at present it is not 
very clear what classificational value is to be ascribed to the latter, although 
one can see the interest attaching, from a philosophical point of view, to the 
recognition of the peculiarities embodied in them. Thus, Mr. Kent, in 
establishing his primary groups, has regard, i not so much to the varied 
character of the locomotive or prehensile appendages posssessed by the 
representatives of this sub-kingdom, as to the nature of the oral apparatus 
or systems subordinated to the function offfood-ingestion.’ In the first and 
lowest of these sections food is 1 incepted indifferently at any point of the 
periphery or general surface of the body these are called Pantostomata , 
and the Rhizopods may be taken as typical examples of them, although 
sundry flagellate Infusoria are included in the group. In the second section, 
although there is no true mouth, the inception of food is performed by a 
discoidal area occupying the anterior extremity of the body ; these are the 
Discostomata, and they are represented by the collared flagellate forms and 
by the sponges. The Eustomata have a true mouth, and are best represented 
by the ciliated Infusoria; whilst the Polystomata include only the ten- 
taculiferous forms, such as Acineta. The four classes of Protozoa, however, 
are characterized by their locomotive or prehensile arrangements, — they are 
the Rhizopoda, Flagellata, Ciliata, and Tentaculifera. With the first- 
named class the present work has nothing to do ; the others will be treated 
in detail, and we have in this first part the general description of the 
structural and physiological characters presented by them. 
As may be seen from a previous quotation, Mr. Saville Kent accepts un- 
conditionally the view of the unicellular nature of the Infusoria; but simple 
as this makes them out to be, he finds a good deal to tell his readers about 
their structure and the functions of the comparatively few parts of which 
they consist. Throughout the section of his work dealing with the mor- 
phology of the Infusoria, we find him making full use of the results arrived 
at by previous observers, but these are checked in all cases by his own 
researches, which have been pursued most industriously for many years. 
The same thoroughness of treatment characterizes the exceedingly interest- 
ing section devoted to the consideration of the reproductive phenomena of 
these little creatures, and the important chapter in which the question of 
spontaneous generation is discussed. Here the author again adopts the 
historical mode of treatment ; and, commencing with the results of the earlier 
observers, works up through the investigations of Pouchet and Pasteur in 
France, and of Bastian and Tyndall in England, to those of Dallinger and 
