256 THE AMERICAN NATURALIST. [VOL XXXIII. 
and leather. Much that has been classed as “techno-geography ” 
and “anthropo-geography”’ is included in this memoir under “ cul- 
ture-physiology.” Frobenius has made a decided gain in lucidity 
and directness of presentation of his subject by employing this 
formal nomenclature ; in less skillful hands it might lead to the warp- 
ing of facts to fit them to the plan of research. 
A series of 26 charts accompanies the volume upon which the 
various culture areas are indicated. There is a fascinating appear- 
ance of finality about such diagrams, yet, owing to the many sources 
of error in museum records, from which the charts were made out, 
they must at best be regarded as provisional and incomplete. ‘The 
value of the memoir is enhanced by numerous illustrations in the 
text. FRANK RUSSELL. 
GENERAL BIOLOGY. 
Embryos without Maternal Nuclei.!— By separating by hand 
under the microscope the unfertilized egg of the sea-urchin, Delage 
has obtained one part containing a nucleus and ovicenter and a part 
devoid of them. When these parts were placed in a drop of water 
containing a normal egg and spermatozoa were added, spermatozoa 
entered into all three pieces and all cleaved. The whole egg devel- 
oped the most rapidly, the nucleated fragment came next, and the 
enucleate fragment most slowly. All were carried to the gastrula 
stage ; the embryo without maternal nuclei being of small size and 
having the enteric and blastoccelic cavities nearly obliterated. Thus 
there has been effected the fecundation and development of a frag- 
ment of an egg without egg nucleus and without ovicenter. Delage 
_ draws the following weighty conclusions :— 
1. Itis necessary to reject as too strict the ordinary definition of 
fecundation — the union of the male and female pronuclei. This 
union occurs, but is not the essential phenomenon. 
2. The definition of Fol—the union of two pronuclei and of two 
demi-ovicenters with two demi-spermcenters — must also be rejected. 
It must be rejected also on account of the often observed fact that 
the absence of the ovicenter offers no obstacle to segmentation. 
3. Any theory must be rejected which explains fecundation by the 
saturation of a female nuclear polarity by a male nuclear polarity, 
1 Delage, Yves. Embryons sans noyau maternel, Compt. Rend., 1898. 
