SOME NEW FACTS ABOUT THE HIRUDINEA. 
C. O. WHITMAN. 
A FEw facts and conclusions are here briefly stated in advance 
of several papers on the Azrudinea, which are now nearly com- 
pleted, and which I hope to see published in the third volume of 
this JOURNAL. 
1. The Hirudinea, as a group, are characterized by the posses- 
sion of segmental sense-organs on the first ring of every somite. 
The plan of arrangement is everywhere essentially the same as 
I have already described in detail for the ten-eyed leeches. The 
statement by Mr. Apathy that such organs do not mark the 
somites in Az/astoma is incorrect ; and inexcusably so, as their 
topography has already been made known. I do not deny that 
some forms are found, like Vephelts, Clepsine bioculata, and Pon- 
tobdella, in which the segmental arrangement has been much 
obscured, or perhaps entirely obliterated. It is plain that such 
conditions might be reached in two ways: either by the loss or 
the multiplication of organs. 
2. As the metameric arrangement of these sense-organs charac- 
terizes marine as well as fresh-water and land leeches, and as they 
everywhere agree in certain remarkable details of number, topog- 
raphy, and structure, I am led to believe that the diffuse, or non. 
metameric arrangement, exemplified in Mephelzs and some other 
forms, has been secondarily acquired. Vephelis is an instructive 
example, for it shows an analogous departure from the typical 
arrangement in the multiplication of its testicular organs. The 
lateral-line organs of some fishes and amphibia illustrate the 
same point. Obscuration of the metamerism of organs through 
multiplication is too well known to require further illustration 
here. The presence of well-developed eyes in (Wephelis, seg- 
mentally disposed, points unmistakably to the former possession 
of the ordinary segmental sense-organs. 
3. I have brought together a large amount of evidence to 
prove that in all ten-eyed leeches, including many widely scat- 
