1076 The American Naturalist. [December, 
serves a useful purpose, especially by enabling teachers of biology to 
place before their students a series of illustrations whose fidelity is 
beyond question, and which may serve as a basis for either elementary 
or advanced work in this direction. 
The photographs have been taken from the eggs of the sea-urchin, 
Toxopneustes variegatus Ag. (a classical object for the study of these 
phenomena), taken as a type. The eggs having been cut into extremely 
thin sections sov to sovo inch.) were stained in iron-hemotoxylin, and 
projected by means of the Zeiss apochromatic oil-immersion objective, 
2 mm. focus, at an enlargement varying from 950 to 1000 diameters. 
They have been reproduced absolutely without retouching or modifica- 
tion of any kind. 
Following is a partial list of the points clearly shown in the present 
series:—The ovarian egg, with germinal vesicle, germinal spot and 
chromatin-network ; the polar amphiaster with the “ Vierergruppen ” 
or quadruple chromosome-groups; the unfertilized egg, after extrusion 
of the polar bodies; entrance of the spermatozoon, the entrance-cone ; 
rotation of the sperm-head, origin of the sperm-aster from the middle- 
piece, growth of the astral rays; conjugation of the germ-nuclei, exten- 
sion and division of the sperm-aster ; formation of the cleavage-nucleus ; 
the attraction-spheres in the resting-cell ; formation of the cleavage- 
amphiaster, origin of the spindle-fibres and chromosomes; division of 
the chromosomes, separation of the daughter-chromosomes; structure 
and growth of the astrosphere; degeneration of the spindle; formation 
of the “ Zwischenkoérper ;” origin of the chromatic vesicles from the 
chromosomes; reconstruction of the daughter-nuclei; cleavage of the 
ovum ; the two-celled stage at several periods showing division of the 
archoplasm-mass, “ attraction-spheres”’ in the resting-cell, formation of 
the second cleavage-amphiasters. 
The explanatory text comprises a simple introductory account of the 
general history of the subject (for the use of students and general 
readers), with a number of figures, mostly original, but a few copied 
from Boveri. In the descriptive part a more critical description of the 
photographs is given, with drawings illustrating every stage shown. 
The atlas will be of great utility to embryologists and biologists in 
general, and the execution will satisfy the student, as worthily illustrat- 
ing the text. The reputation of the author guarantees the accurracy of 
the work. 
A Delightful Book on Butterflies.,—In these excursions into 
5 Frail Children of the Air. By Samuel Hubbard Scudder. Houghton, Mifflin 
& Co., Boston, 1895. Price $1.50. 
