352 The American Naturalist. 
EMBRYOLOGY. 
Experimental Embryology.—Two interesting pieces of work 
employing experimental methods have been recently published by Dr. 
T. H. Morgan. The first? appears to be but a preliminary account to 
be followed by more detailed illustration. The second’ is complete and 
illustrated by figures drawn by the associated author Umé-Tsuda. 
The former deals with the echinoderm—the latter with the frog-egg. 
In the sea-urchin Arbacia punctulata minute fragments of the eggs 
may be fertilized and undergo cleavage, but there is no evidence that 
fragments develop unless they have part of the female pronucleus. 
Hence Boveri’s experiments‘ upon the cleavage of e-nucleated fragments 
are to be regarded with doubt. 
When the eggs are pressed, after the method of Driesch, there is 
evidence that the place of formation of the micromeres is pre-determined, 
and not localized by intersection of the actual first and second planes 
of cleavage since it may be where the first and third furrows cross. 
A repetition of Loeb’s experiments’ shows that the action of an 
increased strength of sodium-chlorid in the sea water is to stop not only 
the external but also the internal or nuclear phenomena of cleavage, 
contrary to Loeb’s notion. 
In the starfish Asterias forbesii it seems that shaking the eggs 
hastens the maturity processes! Bee 
he most remarkable part of the paper is the evidence pointing 
strongly to the conclusion that the eggs of the above star-fish may be 
fertilized by the sperm of the above sea-urchin, “ two animals belonging 
to entirely different ‘ Classes’ of the animal kingdom ” ! 
In the second paper the vexed questions of the orientation of the 
embryo, the place and manner of closure of the blastopore and the 
related idea of concrescence are approached not only from direct study 
of living eggs but from the examination by sections and surface 
views of eggs that have been injured by needle-thrusts or modlie® 
retarded, in development by action of certain salt solutions. Many 
important details hitherto overlooked are made plain and some interest 
‘Edited by E. A. Andrews, Baltimore Md: to whom communications may be 
ddressed. 
? Anatomische Anzeiger IX. 
5 See American Naturalist, April, 1893. 
