THE LEECHES OF JAPAN. 345 
trés vasculaires, or cet animal abandonne spontanément les 
eaux en plein jour. [ls sont beaucoup moins développés dans 
PAulastome qu’on ne voit guére errer sur la terre pendant le 
jour, mais seulement a l’aurore ou au crépuscle. 
“Les Hirudinées, qui n’ont point la faculté d’arroser eas 
peau, n’abandonnent jamais les eaux ot elles vivent; telles 
sont les Nephelis (Erpobdelles) et les Clepsines ou Glos- 
siphonies, qu’ou pent conserver indéfiniment dans des vases 
ouverts.” 
While I fully concur in the opinion that the nephridia aid 
the respiratory functions by helping to keep the skin moist, I 
have found no satisfactory evidence that they assist the work 
of digestion in the manner indicated above. The quantity of 
fluid that escapes from the Land Leech during the process of 
sucking, certainly does not exceed the capacity of the nephri- 
dial vesicles, and hence I see no reason to suppose that the 
more watery and less nutritious portions of the imbibed blood 
are collected and discharged by the nephridia with a rapidity 
that would imply a constant current from the “ stomach ” to 
the exterior through the nephridial ducts. The vesicles are so 
placed with respect to the ceca of the stomach that the 
maximum expansion of the former is correlated with the 
minimum distension of the latter, and vice versa; so that if 
the vesicles are full when the Leech begins to fill itself with 
blood, their contents would probably be expelled in slow but 
steady streams issuing at the nephridial pores. As the gradual 
distension of the ceca would seem to be quite sufficient to 
account for the escape of the nephridial fluid, it is probable 
that the muscles belonging to the walls of the vesicles would 
remain quite passive during the process, their activity being 
reserved for occasions of need such as might arise during a 
dry season or in the perambulations of the Leech. 
If the vesicles serve the end supposed, it is evident that 
there must be some correspondence between their size and the 
1 «Recherches sur lorganisation du systéme vasculaire dans la Sangsue 
médicinale et l’Aulastome vorace,’ Paris, 1862, pp. 28—30. The same in 
‘ Ann. des Sci. Nat.,’ ser. 4, Zool., xvii, pp. 197—199. 
