1889.] Psychology. 739 
the blastoderm comprehends twelve micromeres and twenty macro- 
meres, eight of the former being parted from eight of the micromeres. 
By this method of parting off micromeres, the latter at the end of 
segmentation are more than three hundred in number, and form a 
plaque with the smaller micromeres in the centre. The peripheric 
zone of the blastoderm occupied by the macromeric segments or 
blastocones, becomes transformed into a special thin bed which inter- 
calates itself between the embryo and the vitellus, and is called by 
Vialleton the perivitelline membrane. Meanwhile a division of the 
micromeres or blastomeres perpendicular to their height produces a 
deeper layer of cellules — a mesoderm. Thus the egg at this stage 
consists of: (i) the ectoderm, which forms a circular plate composed 
in its centre of a single layer of cellules, but around its edge of several 
layers, produced by delamination at the expense of the superficial layer. 
(2) Of the mesoderm {pars) represented by the deeper beds of the 
borders of the blastoderm ; and (3) by the perivitelline membrane or 
primitive endoderm. The border of the blastoderm then parts into a 
clear portion which becomes the vitelline sac, and an interior embry- 
onal area. By secondary determinations, the ectoderm afterwards 
furnishes additional elements to the mesoderm. The entoderm, usu- 
ally formed at an early stage, does not show itself in the Sepia until 
the eyes and pallial folds have been sketched out; and its development 
is very rapid, and seems to be formed at the expense of the perivitelline 
membrane. 
PSYCHOLOGY. 
The Psychic Life of Micro-Organisms.'— M. Alfred Binet, 
one of the most eminent representatives of the French School of Psy- 
chology, has presented in the above work the most important results of 
recent investigations into the world of micro-organisms. The subject 
is a branch of comparative psychology little known ; as the data of 
this department of natural science lie scattered for the most part in 
isolated reports and publications, and no attempt has hitherto been 
made to collate and present them in a systematized form. 
iThe Psychic Life of Micro-organisms. A Study in Experimental Psychology. 
By Charles Binet. Translated from the French by Thomas McCormack, with a preface 
by the author written especially for the American edition. Chicago : 1889. The Open 
Court Publishing Company. Cloth, 75 cents. Paper, 50 cents. 
