THE GASTRULATION AND EMBRYO FORMATION 
IN AMIA CALVA. 
BY 
ALBERT C. EYCLESHYMER AND JAMES MEREDITH WILSON. 
From the Anatomical Laboratory of St. Louis University. 
WitH 4 DOUBLE PLATES. 
In an earlier paper entitled “The Egg of Amia and Its Cleavage,” 
Whitman and Eycleshymer, 96, described the development from the time 
of fertilization up to and including the late blastula. The present paper 
is a continuation of the earlier study, and deals with the changes taking 
place between the late blastula and the time when the tail of the embryo. 
becomes free from the yolk; that is, from the time of the late blastula 
until the time when most of the organs are laid down. 
The material was killed in Flemming’s fiuid, Perenyi’s fiuid, chrom- 
osmic acid, picro-acetic acid, picro-sulphuric acid and corrosive subli- 
mate-acetic acid. For surface views, chrom-osmic acid gives most perfect 
pictures; the osmic acid blackens the lines of cleavage so that they stand 
out in bold relief. Another excellent method for surface study is faint 
staining with Delafield’s hematoxylin which may be employed after any 
of the above-named fixing solutions. ‘The best serial sections have been 
obtained after fixation in picro-acetic acid. Owing to the crumbling of 
the yolk we have been compelled to use celloidin as an imbedding mass. 
Serial sections were made after the method described elsewhere by the 
senior author, g1. Staining tm toto is best accomplished by using 
Czoker’s alum-cochineal for from twenty-four to forty-eight hours. 
Staining in section with Mayer’s hemalum and alcoholic carmine has 
proved very satisfactory. . 
So far as the writers are aware, but two papers have been published 
dealing with the phases of development under consideration. Both of 
these appeared in 1896. The first was published by Sobotta and contains 
a fairly accurate, but incomplete, description of the gastrulation stages. 
The illustrations, however, are few and highly diagrammatic. The sec- 
ond was written by Bashford Dean and is more extended, but less ac- 
curate. Dean’s descriptions unfortunately were based upon the errone- 
AMERICAN JOURNAL OF ANATOMY.—VOL. V. 
