180 General Notes. 
large type, and with illustrations, which leave little to be desired. 
While the purpose of the work is the same as that of Kélliker’s 
Grundriss, viz., for medical students, it presents certain admirable 
features not met with in the just-named classical and beautiful work 
of the venerable savant who holds the chair of anatomy in the Uni- 
versity of Würzburg. The wonderful and accurate figures which 
adorn the pages of Kölliker’s writings on embryology are no less 
attractive than the luminous style in which his expositions are 
couched. But in the Grundriss only two types are appealed to— 
viz., the Bird and Mammal, in order to unravel the intricacies of 
embryology as applied to the needs of the medical man. 
With larger opportunities for study, and as the author of many 
classical contributions to the embryology of the lower types as well 
as through studies upon the maturation and fertilization of the egg 
in various types, Dr. Hertwig approaches his subject equipped with 
a range and profundity of knowledge not surpassed by any recent 
writer. His studies in experimental embryology—during which 
e, in association with his no less distinguished brother, Richard 
Hertwig, reached results of the most startling significance in caus- 
ing multiple impregnation of a single ovum by previous immersion 
in dilute solutions of narcotics or anesthetics—are still fresh in the 
minds of specialists. His no less interesting studies upon the 
phenomena of fertilization of the egg in echinoderms entitle him to 
rank amongst those pioneers of modern embryology who have given 
us a basis for a rational theory of heredity, founded, not upon 
abstract speculations, but upon carefully observed facts. 
Through the observation of these facts by Hertwig and others it 
has been possible also to enunciate the doctrine of the continuity of 
germinal plasma and the laws of geotropy of the ovum; while his 
Ceelom theory, published in 1881, has already borne fruit in the 
admirable English treatise of Professor Haddon, which was noticed 
about a year since in this journal. This cælom theory supplements 
that of the now universally accepted gastrula, and makes it possible to 
present the facts of embryology in such a manner as to render their 
comprehension easy and significant. While the protective coverings 
of ova—i.e., the primary and secondary investments of the eggs of 
various types—have not been as fully discussed as they might have 
been, and the existence of a third or tertiary system of deciduous 
investments, derived from the segmenting oyum itself in the higher 
forms, has not hgen perhaps clearly recognized, on the whole the 
work commends itself as the most satisfactory manual which has 
yet appeared for. those who have not the time to enter upon a special 
course of study in this branch of scientific discipline. 
The author has succeeded, in the compass of two hundred pages, 
subdivided into thirteen chapters, in presenting in a novel and in- 
teresting manner what it is essential that the young naturalist, or 
medical student should know of the sexual elements; the matura- 
