CHONDROCRANIUM OF EUMECES 1 
The present investigation was commenced under the super- 
vision of the late Prof. Ernst Gaupp in the Comparative Ana- 
tomic Laboratory of the University of Freiburg, Prof. Robert 
Wiedersheim, director. I wish at this time to express my hearty 
appreciation of the courtesies, scientific and personal, which 
were extended so freely during my stay in Freiburg by Professor 
Wiedersheim, Professor Gaupp, and the other members of the 
staff. 
During the later prosecution of the work I have enjoyed the 
hospitality of the Lake Laboratory of Ohio State University, 
the Zoological Laboratory of Harvard University, and the Ma- 
rine Biological Laboratory at Woods Hole. My thanks are due 
to Prof. Herbert Osborn, Prof. E. L. Mark, Prof. Frank R. 
Lillie, and their associates for their many favors. 
I have also been materially assisted by several of my advanced 
students in Ohio Wesleyan University, and would especially 
thank Mr. Joseph I. Taggart, Miss Margaret Cole, and Mr. 
Clarence L. Turner for the use of models and unpublished work 
freely placed at my disposal. 
And, finally, I wish to record my indebtedness to the Ohio 
Academy of Science for a grant from the Emerson McMillin 
Research Fund, which has provided technical assistance in the 
preparation of drawings and in the work of modeling. Through 
this grant I have been able to avail myself of the services of 
Miss Mabel L. Hedge, whose artistic and accurate drawings are 
reproduced in figures 1 to 8, inclusive. 
2. MATERIAL AND METHODS 
The material upon which this paper is based consists of a single 
brood of eggs collected when the embryos were already consid- 
erably advanced. They were preserved at intervals during a 
period of seventeen days. No data can be given as to absolute 
ages, but the relative ages may be seen from the following tabu- 
lation. The measurements of the table were secured, after 
preservation, by means of a thread laid along the embryo. The 
length of the head is measured from the tip of the snout to the 
