86 PROCEEDINGS OF THE AMERICAN ACADEMY 



POSTSCRIPT. 



lu a very important paper dealing with tiie Ilirudinea,* wliich came 

 to hand only a few days before receiving the proof-sheets of the fore- 

 going paper, Mr. Bourne calls attention to " sensory cells " found in 

 Jlinido medicinalis. The following is all that is said ou the 

 subject : — 



"I do not propose to do more here than draw attention to Fig, 1."), 

 from Hirudo, showing certain of these cells and their connections 

 with nerve trunks. The preparation from whicli this is drawn was a 

 section cut with a freezing microtome and stained in gold chloride. 



" My inability to say much upon this subject is the less to be re- 

 gretted since Leydig t has dealt with these sim|)ler tactile bodies and 

 their derivatives, the eyes, in a most detailed manner." 



Unfortunately Mr. Bourne has not told us from what part of the 

 leech his section was obtained, leaving it entirely uncertain whether 

 it represents a p;irt of a segmental papilla or one of the goblet-shaped 

 organs on the head. As the figure shows none of those peculiar glassy 

 cells, which are found in the eyes and segmental papilhe, it seems 

 probable that it represents one of the simpler goblet-shaped organs 

 which, according to Leydig, % are scattered over the entire cephalic 

 lobe. 



Mr. Bourne does not enter into any discussion upon the nature of 

 the segmental paj^ilUe, and their serial relationship with the eyes has 

 entirely escaped his attention. The method adopted in determining 

 the number of somites (by reference to the nnnibor of ganglia) is of 

 course not reliable at the ends, where a fusion of primitively distifict 

 ganglia has taken place. I have shown that the first thirteen rings 

 constitute six abbreviated somites, wiiile Bourne's method enables 

 him to recognize only eight rings and two somites in the same 

 region. 



* Quart. Journ. IMic. Sci., July, 1884, p. 434. 



t Vnin Bau des thierischen Kijrpers, 1864, and Atlas. 



t Mull. Arch., 1801, pp. 509, 000, 



