350 Some Phases of the Gastrulation of the Horned Toad 
The egg of Phrynosoma stands in closer relation to the lower vertebrates 
than any other amniote in that the protoplasmic pole of the egg seems 
less encumbered with yolk, the blastoderm at least is so elevated that 
processes going on in it are quite as independent as in the Amphibian egg. 
We may say that the development of this iguanid is a link in the chain 
of evidence which supports the Weldon, 83,-Will, 93, theory of yolk 
cleavage wherein the lower layer tends toward the cleavage of the whole 
mass of the yolk as in the Axolotl, and the molluse Bythinia tentaculata, 
figured by Weldon. 
LITERATURE CITED.’ 
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v. 20, pp. 241-261, 17 figs. 
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HerRTWIG, O., 03.—Die Lehre von den Keimblattern. Handb. d. vergl. u. Ex- 
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7A complete bibliography of the embryology of Reptiles is found in Peter, o4. 
