TRANSPLANTATION OF THE LIPS OF THE BLASTOPORE IN 
RANA PALUSTRIS. 
BY 
WARREN HARMON LEWIS. 
From the Anatomical Laboratory, Johns Hopkins University. 
WitTH 5 FIGURES. 
Roux’ first pointed out that the material which forms the embryo of 
the frog is laid down in the black-white ring around the equator of the 
egg, and that the embryo is formed by a process of concurrence in that 
this material grows over the white hemisphere. If this is prevented, as 
in his case of asyntaxia medullaris, a half embryo develops on either 
side of the equator of the egg. Roux’s observations and experiments 
were confirmed by Morgan * in a somewhat similar series of experiments. 
Hertwig* was able to produce the bilateral half embryos by allowing 
the eggs to develop in salt solutions. I have seen many similar forms 
from eggs of rana sylvatica and rana palustris which were kept on ice 
for a prolonged period of time. In such abnormal forms the lips of the 
blastopore which fail to grow over the large yolk plug differentiate into 
these modified half embryos with a central nervous system, muscle, the 
chorda, and the roof of the archenteron. 
More recently Morgan * has investigated the question of the location of 
the embryo-forming substances and concludes that the material is first 
in the upper hemisphere of the developing frog’s egg and is later carried 
downward into the germ ring. 
‘Ueber die Lagerung des Materials des Medullarrohes in gefurchten 
Froschei. Anat. Anz., Vol. 3, 1888. 
*The formation of the embryo of the frog. Anat. Anz., Vol. 9, 1894. 
> Urmund und Spina bifida. Arch. f. mikr. Anat., Vol. 39, 1892. 
*The relation between normal and abnormal development of the embryo of 
the frog, X. A re-examination of the early stages of the normal development 
from the point of view of the results of abnormal development. Arch. f. 
Entwickelungsmech. XIX, 1905. 
The origin of the organ-forming materials in the frog’s embryo. Biol. Bul., 
XI, 1906. 
AMERICAN JOURNAL OF ANATOMY.—VOL. VII. 
