THE, SPHINCTER OF THE TERMINAL. VESICLE 
OF HIRUDO MEDICINALIS. 
ARNOLD GRAF, Pu.D. 
In a preliminary paper (Azuales de la Soctété Sctentifique 
de Bruxelles) H. Bolsius deals with my description of the 
“< sphincter’’ in Hirudo, and promises to prove in a subsequent 
paper that I was wrong in my assertions. 
I stated that the sphzncter, discovered first by H. Bolsius, 
was not the simple structure that the drawings of this author 
would suggest, and gave a drawing of that organ in a paper on 
Nephelts (Beitrage zur Kenntniss der Excretionsorgane von 
Nephelis vulgaris. /enaische Zeitschr. fiir Naturw. Vol. 
XXVIII, N. F. XXI). In this drawing (Pl. VIII, Fig. 8) I 
showed that instead of being constricted by one bundle of 
circular muscle-cells in one place only, z.¢., near the entrance 
tc the terminal vesicle (as H. Bolsius figures it), the terminal 
duct is provided on its whole surface with circular muscle-cells. 
These cells increase in number in two places: first, near the 
communication of the terminal duct with the terminal vesicle ; 
second, near the aperture of the terminal duct to the exterior. 
I treated this fact in my paper as of no great consequence, 
not being directly related to the facts interesting me at that 
time. However, H. Bolsius seems to consider it as of great 
consequence, and asserts that my observation was wrong, 
suggesting that I took the “do0dy muscle-cells’’ for sphincter 
muscle-cells. 
When H. Bolsius informed me by letter that he had written 
a paper on this subject, I looked over my series, almost inclined 
to think that I was really mistaken. But to my great satisfac- 
tion I found that I was right; and I try to prove this by the 
figures in this paper. 
The figures represent successive longitudinal sections through 
the terminal duct, with the sphincter muscle-cells, and are 
drawn with the camera of Zeiss under a magnification of 112. 
