1903-4.] Origin of the Epiphysis Cerebri in the Chick. 167 
(5) Explanation op Figures. 
[The figures were drawn with the aid of Zeiss’s camera lucida apparatus. 
Zeiss’s objective A and ocular No. 3 were employed.] 
c.t., subcutaneous connective tissue; ep., epiphysis; epib ., 
epiblast; l. ep. ev., left epiphysial evagination ; r. ep. ev ., 
right epiphysial evagination ; that ., cavity of thalamen- 
cephalon. 
Fig. 1. Transverse section of the roof of the thalaniencephalon 
in the pineal region. Embryo-chick at the 50th hour of incuba- 
tion. The right and left primary epiphysial evaginations are seen. 
Two germinal nuclei in a condition of karyokinesis are observable. 
The dotted line represents the mesial plane. 
Fig. 2. Transverse section of the roof of the thalamencephalon 
in the pineal region. Embryo-chick at the 60th hour of incuba- 
tion. The right and left primary epiphysial evaginations are 
especially well marked. Several germinal nuclei are seen. The 
mesial plane is represented by the dotted line. 
Fig. 3. Transverse section of the roof of the thalamencephalon 
in the pineal region. Embryo-chick at the end of the 3rd day of 
incubation. The unpaired condition of the epiphysis is shown. 
The presence of two small angular recesses, however, within the 
epiphysial evagination may denote traces of the previously existing 
bilateral condition. 
Issued separately March 17, 1904.) 
