ON THE DEVELOPMENT OF THE FROG. 291 
grey degeneration already referred to. The lips of the blastopore are 
often similarly affected. 
The yolk-cells in the interior degenerate and liquefy ; the liquefied 
mass may burst through the ectoderm and spread over the surface. In 
spite of this, differentiation of the organs of the body proceeds until the 
embryo dies. 
Suckers, gills, tail (often double), pituitary body, optic vesicles, lens, 
infundibulum, auditory vesicle, neural crest. with the vagus and trigeminus 
ganglia ; protovertebre, pronephric thickening, and liver diverticulum are 
all formed. 
The notochord is formed in the same abnormal way as described 
under II., and is bent and twisted. 
(B) Magnesium chloride, magnesium sulphate, and magnesium nitrate, 
cane sugar and dextrose. 
The blastopore closes, though slowly ; the medullary folds do not. 
In the magnesium salts the brain alone remains open ; in the sugars 
the entire length of the medullary folds. The exposed part in all cases 
undergoes grey degeneration. 
All the organs mentioned under (a) are developed, and in addition 
the pericardium, together with a few endocardial cells. 
The tail is better developed and the embryos longer. 
IV. Development is nearly or quite normal ; wrea and sodium sulphate. 
In the former the blastopore and medullary folds close, though more 
slowly than usual. 
The organs already referred to are all formed ; in addition, the heart 
and pericardium, the pronephros, the splanchnoccel, the dorsal aortz and 
posterior cardinal and vitelline veins, and the subnotochordal rod. 
The notochord, though arising in the abnormal fashion observed in 
other cases, has well-differentiated, vacuolated cells. The myotome cells 
are elongate and multinucleate. 
Eventually the embryos die. 
The cells of the central nervous system and of the ectoderm degenerate. 
Mesoderm and yolk-cells swell up ; the latter indeed often produce 
a hernia-like ventral swelling behind the liver, subsequently bursting 
through the body-wall at this point. 
In sodiwm sulphate, on the other hand, development appears to be 
perfectly normal, and'to proceed at the normal rate. The tadpoles will 
live in the solution for many weeks. 
As the work is still incomplete it would be premature to offer any 
explanations or conclusions. At the same time it may be pointed out 
that the facts seem to contradict Bataillon’s assertion that the distorted 
development of the sodium chloride monster is solely the effect of the 
increase in the osmotic pressure. More probably the phenomena are to 
be attributed to the poisonous properties of the substances employed, 
even in the case of the sugars, the differences being due to differences in 
the permeability of the tissues of the embryo. 
The Committee ask to be reappointed in order that the microscopical 
investigation may be brought to a satisfactory conclusion. 
