No. 3.] SOME NEW FACTS ABOUT THE HIRUDINEA. 599 
the sexual pores. The spermatozoa are transmitted in spermato- 
phores, which are planted on any part of the exterior, preferably 
on the back. The gradual contraction of the sperm-case forces 
the contents through the skin in a steady stream that can be 
seen under a magnifying power of 20 diameters. By means 
of sections, I have traced the spermatozoa from the place of 
entrance to within a few millimetres of the ovaries. The same 
mode of copulation occurs in Nephelis, and in Peripatus (Sedg- 
wick). 
THE LAKE LABorATOoRY, Milwaukee. 
Dec. 25, 1888, 
