XVl INTRODUCTION. 
reaching the snow-line, and where one of them at least (hyncholophus nivalis, Heer) 
even surpasses it*, I am inclined to believe that within the tropics Acarids will 
be found at as high an elevation as any other Arthropod group. 
Pror. OTTO STOLL, M.D. 
Kiisnacht, near Ziirich, January 1893, 
* According to the observation of the late Prof. Heer, Rhyncholophus nivalis reaches an elevation of 9580 
feet (top of the Piz Levarone). 
