THE EOCATION (OF-THE BASIS’ OF THE 
AMPHIBIAN EMBRYO. 
ALBERT C. EYCLESHYMER, 
INSTRUCTOR IN ANATOMY, UNIVERSITY OF CHICAGO. 
THE query, ‘From what part of the amphibian egg does the 
embryo arise?” is but a natural outgrowth of the earlier 
researches of Vallisneri, Spallanzani, and Swammerdam. A\I- 
though often answered by later investigators, — Prévost and 
Dumas, Rusconi, von Baer, Reichert, Cramer, Newport, and 
others, — their replies reveal a diversity of opinions. 
The more recent researches of Pfliiger, Roux, O. Schulze, O. 
Hertwig, Morgan and Tsuda, Assheton, and myself have like- 
wise failed to settle the question, but have led to a more precise 
conception of the methods to be employed in attaining a 
solution. The problem might be restated as follows: 
Is the darker (upper) hemisphere of the amphibian egg that 
portion which forms the basis of the embryo, as stated by 
Swammerdam, Prévost and Dumas, von Baer, Reichert, Cramer, 
Newport, and O. Schulze? Or, 
Is the lighter (lower) hemisphere to be regarded as containing 
the basis of the embryo, as held by Pfliiger, Roux, Hertwig, 
Morgan and Tsuda? Or, 
Do considerable portions of both hemispheres contribute to 
the embryonic basis, as advocated by Assheton and myself?! 
In an earlier paper the results of certain experiments on the 
egg of Amblystoma were recorded. These experiments seemed 
to clearly indicate that, at least, the anterior half of the embryo 
of Amblystoma tigrinum differentiates in an area lying between 
the upper pole and the point at which the blastopore first 
appears. 
1 The striking similarity of some of my conclusions, as given in the Journ. of 
Morph., February, 1895, to those of Assheton, published in the Quar. Journ. 
Micr. Sci., December, 1894, compel me to state that a copy of my paper was 
presented to the Biological Faculty of the University of Chicago on Dec. 15, 
1894. The press work was completed when Assheton’s paper was received, so that 
reference to the latter was precluded. 
