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NOTICES OF NEW BOOKS . 
The Free-living* Unarmoured Dinoflagellata. By Charles Atwood 
Kofoid and Olive Swezy. Being Yol. V. of the Memoirs of the 
University of California. 1921. viii 4- 562 pp., 12 plates, 
388 figs, in text. Published by the University of California 
Press, Berkeley, Cal., U.S.A. Price $12.50. 
The dinoflagellates form a very important part of the deep-sea 
meadows, the source of the primitive food supply of the sea, both in 
number of individuals and in the total mass of living substances 
produced. Until quite recently they were but slightly and imperfectly 
known, due, in part, perhaps to their absence from all oceanic deposits. 
Researches, however, which have been carried out on the marine 
plankton have shown that they abound both in neritic waters and in 
the high seas, and range from the tropics to the polar oceans. In 
abundance they are second only to the diatoms, but during their 
periodic maxima they may far surpass the diatoms in the total mass of 
organic material produced and in the rapidity of their development. 
These organisms are the primary and all but universal cause of the 
discoloured seas and of luminescent waters which are wont to occur in 
midsummer round our coasts, and more especially in tropic seas. These 
unicellular organisms may often have a very complex structure, and may 
also be provided with an armour consisting of a series of plates arranged 
in a definite pattern which is constant for the species. There is a 
distinct difference between the apical and the antapical regions of the 
body and also between the dorsal and ventral faces. Besides these 
highly organized forms many of a much simpler structure may be 
obtained by means of the centrifuge — forms in which the cell- wall is 
poorly developed. 
The purpose of this beautiful monograph is to provide a summary 
of our present knowledge of the naked or unarmoured forms, the most 
elusive and least known representatives of this group of protozoa. It 
is based on a study of the marine forms of the San Diego (California) 
region, made at the biological station of the Scripps Institution for 
Biological Research. There are 223 species fully described (or re- 
described) from the point of view of general morphology, histology, 
physiology, history and distribution ; of these no less than 117 are 
described by the authors for the first time. The monograph is fully 
provided with text-figures and twelve coloured plates. 
The investigation of these extremely delicate organisms is fraught 
with great difficulty, as a few moments’ exposure to the brilliant 
illumination under the microscope is sufficient to cause cytolysis, and no 
satisfactory means have yet been devised by which they can be preserved 
for future examination and study. The investigations have thus been 
restricted to the rapid examination of freshly captured living material. 
For collecting the material the ordinary methods proved of no avail, 
