to 
to 
MALL. [Vot. XIX. 
In 1893, Herbst,” while studying sea-urchins’ eggs, observed 
that the action of lithium salts upon them caused the layers 
of the blastoderm to invert in development. The lithium ex- 
periments were repeated by others, including Morgan, upon 
frogs’ eggs, who found that the upper protoplasmic contents 
of the egg fails to move downward, which is followed by a 
complete inversion of the germ layers. The entire upper part 
of the egg sinks into its interior and forms a medullary plate 
which is bent back upon itself. This change in development 
is due to the physical and chemical action of lithium salts, for 
it cannot be brought about by any other means. 
Very recently Stockard* experimented upon Fundulus with 
solutions of lithium chloride and produced monsters which 
developed into quite decent fishes, but at present it is impos- 
sible to compare them with lithium larve of sea-urchins and 
frogs. In these embryos the blastoderm is usually prevented 
from growing downward over the yolk, as is also the case in 
the frog, and therefore bulges as a cap upon the upper part 
of the egg. In stronger solutions of lithium this cap often 
constricts at its borders and finally pinches itself off from the 
yolk and dies. In embryos which survive, the heart beats 
slowly, the eyes often fail to develop, the blood is colorless and 
therefore appears to lack hemoglobin. These characteristics, 
taken with the inability to recover from the lithium effect, 
seem to prove that they are due to chemical causes. 
At present it is difficult to compare the great variety of 
monsters produced in anamniotic with those obtained in 
amniotic animals, for the number of the latter is relatively 
‘small and their description meager. We have a series of 
excellent papers on the production of monsters in the hen’s 
‘egg by Panum,* Dareste> and Féré.6 These authors, how- 
ever, devoted their main discussion to the teratogenic agents, 
*Herbst, Mitth. Zool. Sta., Neapel, 1893, and Roux’s Archiv, 1806. 
» Jour. Ex. Zool., Baltimore, 1906. 
‘Panum, Entstehung d. Missbildungen, Berlin, 1880. 
*Dareste, Recherches sur la production de monstrosités, Paris, 1891. 
*Féré, Cinquantenaire de la Société de Biologie, Paris, 1899. 
