1893.] Embryology. 1099 
Lithium Monsters.—Curt Herbst’ has continued his work* 
upon the action of salts upon echinoderm larve and publishes a full 
account, with careful figures, of the various abnormal or monstrous 
larval forms produced by the action of very dilute solutions of lithium 
chlorid. 
Both Sphærechinus and Echinus give results though Asterius, and 
presumably other animals, act differently or not at all under the influ- 
ence of this salt. 
The eggs are fertilized and then put into sea water containing 2} % 
of the lithium solution. This solution itself is, however, very weak, 
only 3°8 g Li Cl to 100 em hydrant water. 
The blastulas that arise from these eggs have thick walls with the 
inner end of their cells much vacuolated at first, but as they enlarge 
become elongated vesicles with thin walls. This vesicle becomes con- 
stricted into two, more or less separate; one has a thicker wall and 
long cilia, the other a thinner wall and short cilia. Between the two 
an intermediate, connecting vesicle may subsequently be interpola- 
Now it is evident that one of the vesicles, the one with thin cells of 
long cilia represents the ectodermal part and the other vesicle, the 
thick walled one, the entodermal part of a gastrula turned inside out ; 
for there are all transition stages between these double vesicles and 
what the author calls exogastrule. These are evidently gastrulas in 
which the entodermal tube protrudes as a closed, thick walled process 
just as would be formed if the entoderm grew outward instead of 
inward as normally happens. - 
Invagination being due to a rapid growth of a zone of cells on the 
vegetative side of the blastula we need but have the direction of growth 
changed, by the lithium salt, to produce such an exogastrula. If this 
zone of growth extend, under the influence of the salt, more and more 
over the vegetative side of the blastula there will result a more typical 
lithium larvz, or stages between it and the exogastrula. Finally 
some cases arise in which it seems that this zone extends all over the 
blastula ; such larvæ are mere single vesicles of entoderm! There is 
thus à conversion of what would normally form outside and inside, 
ectoderm and entoderm, of the gastrula, into what may be styled ento- 
derm only. : 
The author thus agrees with Driesch in regarding the cells of the 
early larve as omnipotent in their capabilities; they may become 
3Mitth. Zool. Sta. Neapel. II. 
AMERICAN- NATURALIST, March, 1893. 
