REVIEWS. 
347 
His object, and that of Dr. Hayden, in the production of the work, was to 
show observers in the States what a wealth of interesting objects awaited 
their investigation, and to furnish a trustworthy guide-book which would 
enable them to know what had already been done. 
At the same time, we think that the author has indicated (not only here 
but in scattered papers published during the progress of his researches) that 
these lowly organisms are much more generally distributed than was formerly 
supposed. He says : 1 Freshwater Ehizopods are to be found almost every- 
where in positions kept continuously damp or wet, and not too much shaded. 
They are especially frequent and abundant in comparatively quiet waters ; 
clear, and neither too cold, not too much heated by the sun 
They are also frequent in wet bogs and savannas, among mosses, in springy 
places, on dripping rocks, the vicinity of waterfalls, springs and fountains, 
and in marshes, wherever the ground is sufficiently damp or moist to pro- 
mote the growth of algae. They are also to be found in damp, shaded places, 
among algae, liverworts, and mosses, about the roots of sedges, rushes, and 
grasses, or those of shrubs and trees growing in or at the borders of bogs and 
ponds, or along ditches and sluggish water-courses. They are likewise to be 
found with algae in damp, shaded positions in the depressions and fissures of 
rocks, in the mouths of caves, among decaying logs, among mosses and lichens 
on the bark of growing trees, and even in the crevices of walls and pavements 
about old dwellings, and in cities.’ * And to encourage the student to work 
upon this abundant and almost ubiquitous material, he adds that it is a mis- 
take to suppose that a very elaborate microscope is necessary for its examina- 
tion, such an instrument as may foe procured for about 10/. being generally 
sufficient for every purpose. We may add that he gives full directions for 
collecting the animals in various localities. 
Dr. Leidy regards the Rhizopoda (which he accepts in the old sense of the 
term) as including five orders, namely, Protopiasta, Heliozoa, Radiolaria, 
Foraminifera, and Monera. Of the last he candidly admits that he knows no 
freshwater form, unless Vampyrella (here referred to the Heliozoa), which 
Hackel places among his Monera, really belongs to that group. The Radio- 
laria are marine ; of the Foraminifera our author admits one freshwater 
type, Gromia ; and the rest of the forms described by him belong to his 
orders Protopiasta and Heliozoa. The Protopiasta includes the whole of the 
Amoeboid forms, whether naked or shelled ( Protopiasta lobosa), as well as 
the Euglyphoid types (P.JUoso) ; to the Heliozoa are referred Actinophrys 
and Actinosphcerium with the allied forms which have been made the types 
of distinct genera by various authors, and also, as already stated, the genus 
VampyreUa of Cienkowski. The only representative of the genus Gromia , 
described as a new species ( Gromia terricola ), was found with Rotifers and 
other organisms among moist moss in the crevices of pavement in a yard in 
Philadelphia. 
It is impossible to estimate too highly the care and labour that Prof. 
Leidy has bestowed upon the preparation of this splendid work. All the 
forms discovered by him are described in the most careful manner, as regards 
both their form and structure, and their habits ; and the opinions of authors 
* P. 8. Lists of forms obtained together will be found at pp. 289-293. 
