THE ANNALS 
MAGAZINE OF NATURAL HISTORY. 
[THIRD SERIES. ] 
No. 102. JUNE 1866. 
XLIV.—On the Anatomy and Physiology of the Vorticellidan 
Parasite (Trichodina pediculus, Ehr.) of Hydra. By Prof. 
H. James-Crark, A.B., B.S.* 
[Plates VIII. & IX.] 
THERE can be no doubt that a large amount of the diversity of 
opinion in regard to the general and classificatory relations of 
animals arises ‘from the lack of a correct knowledge of the intimate 
structure of the subject under controversy. This is especially 
applicable to the lower forms of life, and above all to the fifth 
and lowest grand division of animals—the Protozoa. Theories 
which are based upon insufficient observations and a misconcep- 
tion of facts not only present .a distorted view of nature, but 
mislead and give a wrong direction to the tendencies and cur- 
rents of scientific research. The theory of the unicellular nature 
of Infusoria—so acutely upheld by the arguments of Siebold 
and Kolliker, and especially by the latter m his papers on the 
Gregarinide+ and on Actinophryst—had no small influence n 
blinding the mental vision of subsequent investigators, and long 
delayed the conclusion (strangely enough, too, seemingly favoured 
by Kolliker himself) that it is not essential to the constitution 
* From the memoirs read (Oct. 18, 1865) before the Boston Society of 
Natural History, vol. i. part 1. Communicated by the author. 
+ Beitrage zur Kenntniss niederer Thiere (Zeitschr. fiir wiss. Zool. Bd. i. 
(1848-49) p. 1. 
{ Das Sonnenthierchen, Actinophrys sol (Zeitschr. fiir wiss. Zool. Bd.i 
(1848-49) p- 198. In some remarks upon Actinophrys which I took occa. 
sion to make at a meeting of the Boston Society of Natural History (see 
Proceedings for September 16, 1863), I stated that the so-called vacuoles 
of the Actinophrys (A. Eichhornii) are “‘true cells with a distinct wall 
about them.” In a new work (Mind in Nature; or, The Origin of Life 
and the Mode of Development of Animals: New York, 1865) just issued 
from the press, I have reiterated this statement, and given still further 
details of the anatomy and physiology of Actinophrys. 
Ann. & Mag. N. Hist. Ser. 3. Vol. xvi. 26 
