834 THE AMERICAN NATURALIST. [VOL XXXII: 
ings, defibrinations, and reinjections. The reformation of fibrinogen 
takes place normally in the absence of the spleen, the pancreas, the 
kidneys, the reproductive organs, and the brain; but only in very 
small amounts if the intestines be removed. Fibrinogen is not formed 
directly from the proteid constituents of the food, for it readily 
reforms after protracted fasting. If leucocytosis be prolonged for 
several days by suppurations, the fibrinogen of the blood increases. 
Fibrinogen is, therefore, probably produced by the decomposition of 
leucocytes, especially those of the intestinal area. As the fibrinogen 
of the blood brings about a contractile fibrillar structure in forming 
a clot, so possibly the fibrinogen of a cell such as a leucocyte may 
be connected with the formation of the contractile fibrils of the asters 
in cell division. Cw Pp 
ZOOLOGY. 
The Rotifera.'— In this, the first part of a proposed monographic 
treatment of the Rotifera, Lund gives the more general results of a 
study which has been conducted on a broad basis. The author has 
undertaken to examine the group from a purely objective standpoint, 
without regard to theories of the primitive nature of the organs of 
the animals, nor of the relationship of the Rotifera to other groups. 
The result is the most valuable contribution to the biology, morphol- 
ogy, and classification of the Rotifera that has appeared for many 
years. 
Lund examines successively the principal structures that may be 
used in classification — the nature of the cuticula, the ciliary organ, 
the mouth parts, the foot, and the sense organs. A strictly objective 
comparative anatomical standpoint, unbiased by previous theories, is 
maintained in this study. The structures in question are traced 
in all their modifications and transitions throughout the group, and 
an attempt is made to discover the primitive condition of each, 
together with the path of evolution in the development of the more 
striking modifications. The cecological value of the organs is 
brought throughout into the closest relation with their structure. 
The result is a classification of the Rotifera differing widely from 
those based on preconceived ideas as to the relationship of this 
group to the Trochophora, or to other groups ; a classification which 
1 Denmarks Rotifera. I. Grundtraekkene i Rotiferernes Okologi, Morfologi og 
Systematik, af C. Wesenberg Lund. Kjøbenhavn, 1899. 145 pp., 2 plates. 
