460 
HENRY F. NACHTRIEB 
Fig. 8. Photographs of a horizontal or transverse section of several groups of 
primitive pores showing the distribution of the pigment cells, the lymph spaces 
and blood vessels among the primitive pores. The section passed through the 
pores a little above the plane of the floor of most of the pits. The photograph 
was partially inked to bring out certain features more clearly than others. 
Photographs w ith a Zeiss aa, plate about six feet from the object. Figure one-half 
the size of the photograph. 
Fig. 9. Photograph of a longitudinal section of four primitive pores showing the 
general form of the pits. All the blood vessels, excepting the one next to the 
number of the figure are empty. A small nerve is shown at the left of the number. 
The photograph was partially inked, and the reproduction here is one-half the size 
of the original. 
The dimensions of the pits were determined with, a Zeiss Screw Stage Microm- 
eter. The photograph was made with a Zeiss C objective, the plate about five 
feet from the slide. 
of branchlets like those of the lateral line. I have never found any 
of the branches or branchlets of the lateral line system in any way 
in communication with a primitive pore. The primitive pores 
are not and, I believe, never have been in communication with the 
lateral line system. Incidentally it may be remarked that the 
lateral line of the Polyodon shown in fig. 5 is typical, and effectively 
