292 General Notes. [March 
forty-six families were described and the principal genera enu- 
merated. His paper also contained a tolerably complete bibliog- 
raphy of the subject, the size of which is shown by the fact that 
it embraced the titles of fourteen hundred and forty-six papers. 
The systematic position of the sponges was also discussed, 
EMBRYOLOGY. 
Haddon’s Introduction to the Study of Embryology.’ — 
This new work, now in press, is apparently designed to give the 
student a comprehensive outline of the science of embryology 
in a moderate compass, with such illustrations as will enable him 
to appreciate the fundamental similarity of many of the stages of 
e embryos of the different classes and orders of the Metazoa as 
represented by specific forms. A manual of this sort has been 
very much needed for the class-room, e monumental treatise 
of Balfour, in two volumes, already needs revision, so fruitful 
have been the labors of active embryological workers within the 
last five years, or since its completion. That activity itself has 
been very largely due to the stjmulus given to ontogenetic re- 
search by that singularly endowed genius, lost to us before he 
had had time to develop the germs of the great generalizations 
and suggestions which are so lavishly strewn through the pages 
of his great work. Balfour’s large work, also, is not adapted to 
` the purpose of a class-room manual, and can only be used as a 
book of reference or as a guide to the advanced student. In the 
first volume, and the early part of the second, the groups are 
treated of separately and not directly and comparatively, so that 
it is not well adapted to serve as a text-book for the laboratory 
in elementary wor ther elementary text-books use only ex- 
tremely modified forms, such as the chick and the mammal, as 
types ; other lower groups being scarcely alluded to. This tends 
to develop a bias in the mind of the student which it is hard for 
him to shake off, and in extending the range of his studies he 
finds himself almost unwittingly trying to attempt to apply his 
knowledge of the development of the higher forms to that of 
the lower, with the result that he becomes confused in making 
his comparisons. To overcome this difficulty we need an ele- 
mentary work which will contrast the higher and lower type at 
«ätea by Dr Jorns A. TENEN 
u Introduce of E ology, Alfred C. Had M.A., 
Professor in ihe Royal College of Science, Dublin in, K a ee a 
