INVEKTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 289 



The volume is illustrated by 48 plates, with crowded coloured 

 figures. It is adapted to the uninitiated as well as to adepts in 

 the science. Dr. Leidy says : " In the course of its preparation I 

 have always had my pupils in mind, and I shall be glad if it serves 

 as an additional aid to their studies." There is a bibliographical 

 appendix containing the names of authors of works and memoirs on 

 living Ehizopods, and lists of all the species they describe, together 

 with the synonymy, so far as giving the names of the same adopted 

 by Dr. Leidy. 



Dr. Leidy's experience enables him to give important information 

 as to the localities of the Ehizopods, and the best method of collecting 

 them. The following are a part of his observations on these points. 



Localities of Bhizopods. — "Fresh-water Rhizopods are to be found 

 almost everywhere 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 nor too much 

 heated by the sun, such as lakes, ponds, ditches, and pools. 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 damj) 

 or moist to promote the growth of algae. They are also to be found 

 in damp shaded places, among algfe, liverworts, and mosses, about 

 the roots of sedges, rushes, and grasses, or those of shrubs and trees 

 growing in and at the borders of bogs and ponds, or along ditches and 

 sluggish watercourses. They are likewise to be found with alga) 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 pave- 

 ments about old dwellings and in cities. 



" The favourite habitation of many kinds of Ehizopods is the light 

 superficial ooze at the bottom of still waters, where they live in asso- 

 ciation with diatoms, desmids, and other minute alga?, which form the 

 chief food of these little creatures. They never jienctrate into the 

 deeper and usually black mud, which, indeed, is almost universally 

 devoid of life of any kind. 



" Ehizopods also occur in the flocculent materials and slimy matter 

 adherent to most submerged objects, such as rocks, the dead boughs 

 of trees, and the stems and leaves of aquatic plants. A frequent posi- 

 tion is the under side of floating leaves, such as those of the i)ond-lily, 

 Nymphcea odorata; the spatter-dock, Nuphar advena ; and the Nelmnbo, 

 Nelumhium luteum. Certain kinds of Ehizopods, especially the 

 Heliozoa or Sun-animalcules, are most frequent among floating 

 plants, such as duck-meat, Lemna ; hornwort, Ceratophyllum ; 

 bhiddcrwort, IJtricularia ; and the various confervas, as Zi/ijncma, 

 Spiroriyra oscillntoria, and the water-purse, Hydrodictyon. 



"In no other position have I found Ehizopods of tlie kind under 

 considcriition in such profusion, number, and beauty of form as in 

 sphagnous bogs, living in tlio moist or wet bog-moss, or S}ih(t(inum. 

 Sometimes I have found tliis particular moss actually to swarm with 

 multitudes of these creatures of the most extraordinary kinds and iu 



VOL. III. U 



