1880. | A Sketch of Comparative Embryology. 249 
discussions in a long series of special papers. Prof. Haeckel’ has 
written a great deal upon the: gastrula and its significance, and 
has published several popular works on embryology. Unfortu- 
nately, he is inaccurate and untrustworthy to a degree surpassing 
any other scientific writer I can recall, for on almost every page 
are mistakes it requires little knowledge to detect. He is, there- 
fore, utterly useless to the beginner. I mention this, not alone as 
my personal conviction, but also as the judgment of competent 
and distinguished critics, some of whom are even more severe in 
thein condemnation, For these considerations I shall not quote 
Haeckel as an authority. The references to some of the special 
papers I have consulted will be given hereafter. 
E. GENERAL PAPERS ON THE GERM LAYERS. 
31. Agassiz, Alexander. Critique de la Gastræa theorie. (Traduit par Schneider.) 
Arch. Zool. expt. Tome tv, p. 1x (1875). Also Mem. Amer. Acad. x, No. 3. 
32. Lankester, E. Ray. On the Primitive Cell Layers of the Embryo, etc., etc. 
Ann. and Mag. of Nat. History, Vol. x1 (1873), p. 321-338. 
- Notes on the Embryology and Classification of the Animal Kingdom, etc. 
Quart. Journ. Micros. Sci. 1877. p: 399- 
34. Minot, C. S.. Recent Investigations of Embryologists, etc. Proc. Boston S. N. 
H. Vol. xIx, p. 165. (A brief summary.) 
35- Moquin-Tandon. De quelques applications de Embryologie à la classification 
méthodique des animaux. Ann. Sci. Nat. Zool., 11 (1875), Art. 7. 
- Salensky. Bemerkungen über Haeckel’s Gastræatheorie. Archiv f. Naturges. 
Bd. 1. Jahrg. 40 (1874). 
- Semper, Carl. Kritische Gänge. No. 11. Die Keimblätter theorie. Verh. 
phys, med. Gesell. Würzburg. Bd. (1873), p. 222. 
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! “ Professor Hacckel’s principal articles on the Gastrula are to be found in the 
Jena Zeitschrift für Naturwissenschaften, Band. VII, p: 1, and Biologische. Studien, a 
tes Heft. 1877. Haeckel introduced the term Gastrula, and his writings and spec- 
ulations have afforded a powerful stimulus to waits”: research.” seis 
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