No. 416.] REVIEWS OF RECENT LITERATURE. 687 
study. This is the principal failing in Brown’s Physiology for the 
Laboratory (Boston, Ginn & Co., 1900, viii + 167 pp.), which, how- 
ever, is so well balanced in other respects that it deserves to be in 
the hands of the teacher if not in those of the pupil. 
Kelly Vena. Zeitschr., Bd. XXXV, p. 429) has pointed out that 
calcic carbonate occurs in nature in five forms: calcite, aragonite, 
ktypeite, conchite, and amorphous calcium carbonate. Of these 
calcite and conchite are the only ones found abundantly in organ- 
isms. Conchite is probably slightly more soluble, harder, and has 
a higher specific weight than calcite. Both forms occur through- 
out the animal series ; thus calcite is the mineral component of the 
shells of echinoderms, brachiopods, crustacea, bryozoa, of the cal- 
careous spicules of sponges, of the ear stones of fish and amphibia, 
and of the eggshells of mollusks, most reptiles, and birds ; conchite 
is characteristic of the skeletons of most stone corals, and the shells 
of many mollusks. 
Steinach and later Magnus have shown that the iris of a frog’s 
eye will contract when stimulated by light, even after the eye has 
been removed from the animal. Steinach believed this to be due to 
the direct action of light on the sphincter muscle ; Magnus attributed 
it to a short nervous reflex arc within the eye. Guth (Archiv ges. 
Physiol., Bd. LXXXV, p. 119) finds that frog eyes show this reaction 
fully two weeks after their removal from the animal,—a period much 
longer than that during which other organs containing reflex arcs, 
like the intestine, remain active. Moreover, pieces of the edge of 
the iris as well as minute isolated groups of muscle fibres from the 
Sphincter pupille contract on illumination. As the latter were 
shown on microscopical examination to contain no ganglion cells, it 
must be admitted that Steinach's contention that the muscles of the 
ms are capable of being stimulated directly by light is correct. 
BOTANY. 
Recent Papers on Algae. — (Comére, Joseph. Les Desmidées 
sal v Paris, 1901, 222 pp., r6 pls.) In the introduction the 
Mis States his doüble purpose in writing this work ; first, to give as 
account as possible of our present knowledge of the desmids ; 
Second, a manua] for the study and determination of the French 
