602 
till within the last ten years, and have not found their 
way into general treatises and text-books before the 
present occasion. 
With Mr. Kent’s views as to the affinities of the dif- 
ferent classes of Infusoria it is not necessary to agree in 
order to appreciate the value of his work in general. 
The view is maintained in the “ Manual” that the 
Sponges are genetically related to the Flagellata, whilst 
an opinion is quoted to the effect that the Ciliata are re- 
lated to the Turbellaria. Without discussing the grounds 
for either of these views, we must simply express our 
entire disagreement with Mr. Kent, who is not (it seems 
to us) so happy in these speculations as in the more sub- 
stantial portion of his work. The woodcut on p. 477, 
vol. ii., comparing the disposition of the ciliated bands of 
various Infusoria with that of the similar ciliated bands 
of various larve of higher animals, is exceedingly instruc- 
tive and useful. It serves to point out the close similarity 
in form and disposition which such ciliated bands may 
assume in organisms totally unrelated to one another in 
the genealogical sense. Mr. Kent, however, takes the 
view, which we think will not be shared by many zoologists, 
that there is a deeper significance in the occurrence of 
these similar modifications of similar structures in forms 
so widely apart as unicellular Protozoa and multicellular 
Molluscan, Polyzoan, and Echinoderm larve ; according 
to Mr. Kent they indicate “ affinity,” “ phylogenetic con- 
nection,” and ‘‘ biogenetic relationship.” In every direc- 
tion Mr. Kent detects possible instances of such affinity, 
which he sets forth in a tabular form on p. 479 ; but it is 
not always quite obvious what Mr. Kent means when he 
speaks of certain Infusoria as “ prototypes of’’ and as 
“foreshadowing’”’ higher organisms. Had he confined 
himself to drawing attention to the remarkable parallelism 
or homoplasy presented by Infusoria on the one hand, 
and certain higher organisms on the other, we could have 
appreciated his capacity for detecting structural coinci- 
dences. But it appears to be Mr. Kent’s opinion that the 
Holotrichous Ciliata are the forefathers of the Annelida, 
which are a/so traced by him to the Peritricha. The 
latter have (according to Mr. Kent) given rise to the 
Polyzoa, Mollusca, and Echinoderms ; the Hypotricha 
are the ancestors of the Rotifera and of the Arthropoda ! 
whilst the Tentaculifera are the progenitors of the Ccelen- 
terata and the Choano-flagellata of the Sponges. 
Mr. Saville Kent is no doubt entitled to hold and to 
promulgate an opinion on these matters, but we regret, 
inasmuch as his opinion is a very singular one, that he 
should have allowed it to take a prominent position in 
this “ Manual.” 
Upon the question of spontaneous generation Mr. 
Kent is in accord with the prevalent doctrine, and gives 
a clear exposition of the history of the discussion of the 
subject, and so exhibits the importance of the researches 
carried on by Messrs. Dallinger and Drysdale upon the 
reproductive process in certain flagellate Infusoria, and 
the power of the ultra-minute germs of these Flagellata 
to resist the destructive influence of high temperatures. 
With regard to the normal generation of Infusoria Mr. 
Kent is not so satisfactory. He distinguishes Fission, 
Gemmation, Sporular Multiplication, and “ Genetic” Re- 
production—the latter term being, without explanation, 
applied to sexual reproduction. Our author clearly has 
NATURE 
| April 26, 1883 
not—amongst his numerous and widespread researches 
upon the Infusoria—devoted any time to a personal in- 
vestigation of the phenomena of conjugation and rejuve- 
nescence amongst the Ciliata. The account which he 
gives of the work of Engelmann and Biitschli is meagre 
in comparison with the space which he has devoted to 
speculative digressions, and we find no figures illustrative 
of the exceedingly important results attained by those | 
authors. In view of the great biological interest of the 
phenomena of conjugation in unicellular organisms gene- 
rally, this is a serious omission. It is a mistake to have 
introduced the bygone error of attributing sexual repro- 
duction to the Infusoria into this work at all,as Mr. Kent 
has done by the heading of his paragraph. Fission, 
gemmation, and possibly spore-formation preceded at a 
certain period in the family history by conjugation, 
constitute all that is own to occur in Infusoria. 
Mr. Kent makes too much of the isolated cases 
of spore-formation among Ciliata which stand upon 
good evidence. Admitting them as cases of spore-forma- 
tion (that is of multiple fission), it is not possible to use 
them in support of the exploded view as to the production 
of embryos in the Ciliata by the breaking up of the nucleus 
after conjugation. Mr. Kent still clings to this notion of 
a special and peculiar formation of embryos within the 
parent ciliate Infusorian after, and as the immediate 
result of, conjugation, but he does not adduce any new 
fact in support of it. There is no reason adduced by Mr. 
Kent for regarding the nucleus of Infusoria as anything 
more than acell-nucleus, and one is surprised to find that 
he should express so strong a disagreement with Biitschli 
as to the fate of the cast-out fragments of the nuclei of 
conjugated Ciliata, when he does not detail to us any 
original observations made by him upon the process in 
question. The cast-out fragments of the nucleus of the 
conjugated Ciliate possibly have the same significance 
(Mr. Kent calls it an “unprofitable destiny,” p. 98) as the 
cast-out preeseminal apoblasts or “ directive corpuscles ’” 
of an ordinary egg-cell. 
Undoubtedly the best part of Mr. Kent’s book, and 
one which will prove of constant value to that large body 
of working naturalists who are scattered throughout 
English-speaking lands, who delight to follow with care 
and accuracy, by the aid of the microscope, the forms 
and life-histories of the minute beings first made known 
by Mr. Antony van Leeuwenhoek, is that which contains 
the systematic description of every known species of 
Infusoria. 
Accuracy is one of the first requisites in any attempt 
at scientific work, and Mr. Kent’s descriptions and 
figures will enable numberless good observers in country 
places and small towns where there are no libraries con- 
taining the big books of Stein and Ehrenberg to 
accurately identify the organisms which they observe. By 
familiarity with Mr. Kent’s book such an observer will be 
able to tell whether he has observed a new species or a new 
fact abouta known species, and he will rise at once from 
the position of an isolated spectator of the curiosities of 
microscopic life to that of a possible contributor to the 
world’s knowledge of animal structure, a fellow-worker 
with all the naturalists of civilised humanity. It is an 
excellent thing for the cause of science in England, and 
an excellent thing for other good causes too, that there 
