PLATE XxX. 
Fia. 1. — Terra upon surface of tongue of snail (Helix pomatia) ; 
magnified 80 diameters by Collins’s one-inch objective ; in balsam ; 
heliostat. 
Fic. 2.— Tracuea of silkworm, magnified 15 diameters by 
Tolles’s 2-inch objective ; in balsam ; heliostat. 
