On the gustatory organs of some of the mammalia

and Dr. J. N. Hall, of Sterling, Colorado, for their kindness in .supplyingme from time to time with valuable specimens.The greater part of the material had been kept in dilute or ordinary spirit.Of the remaining specimens, some were hardened in absolute alcohol, others in osmic acid, and still others in Muller's fluid, either alone or in a mixture of Muller's fluid and alcohol in various proportions.T h e parts of the specimens intended for microscopical examination were embedded in celloidin, and for staining the tissues the usual reagents were employed.A table containing some comparative data respecting the gustatory structures of the forms considered in the following pages is appended to the paper. THE TOXGUE OF Didelphys viqiniana.I examined several tongues of Didelphys, most of them from adult animals.All of the specimens had been hardened in spirit before I received them. Gtweval Descr9tion.-The organ measures 75 mm. in length, 18.5 mm. in breadth, and 13 mm. in thickness.Anteriorly it is free from the fraenum lingua: for 34 mm.T h e under surface is smooth and marked by a longitudinal median ridge extending from the frznum to the tip.On either side of the ridge is a wide but shallow groove.T h e tip, which is somewhat obtuse, is bordered by a delicate fringe of simple filiform papillze, the latter being probably tactile in function.T h e upper surface is impressed by a number of transverse furrows, corresponding to the roof of the palate.Anteriorly it is covered with closely packed compound filiform papillz, to be presently described.The fungiform papillae are of fair size, and appear to be normal in structure.They are not, however, very numerous, and, as No. 2.1 O N THE GUSTAlORY ORGANS.153usual, are smallest about the tip.The circumvallate papillae are three in number.They are arranged in an isosceles (or more rarely an equilateral) triangle, the base of which measures 4.6 mm.The apex of the triangle is turned towards the epiglottis, and is distant some 12 mm.from the base of the tongue.The posterior papilla is situated directly in the middle line of the organ, and is much larger than the anterior papilk.T h e region behind the triangle formed by the circumvallate papillae lacks the usual fleshy elevations, and is quite smooth; the immediate area around the papillze, however, is more or less papillate.T h e lateral organs of taste (papillae foliatx) were so effectually concealed that the superficial examination of the tongue failed to reveal their presence.At each side of the tongue, just above the line of union of the upper and lower surfaces, is a fringe of rather coarse filiform papillze, curving upwards, inwards, and backwards.T h e fringe terminates before reaching the base of the glosso-palatine arch.T h e tongue of a young Didelphys presented some points of interest.This organ was 19 mm. in length and 7 mm. in breadth.T h e dorsum was marked anteriorly by a longitudinal mesial raphe.T h e raphC disappeared about 1 2 mm.from the tip.T h e tip was rounded, and fringed with simple papilk as in the adult organ.T h e circumvallate papillz were arranged in the usual triangle, but were very closely set and very near the base of the tongue.T h e lateral fringe of filiform papillze at the back of the tongue was well marked.The Mechmzicnl PapiZh.-The general surface of the tongue, anterior to the triangle formed by the circumvallate papille, is covered with compound filiform papillae.Interspersed among them are a lesser number of filiform papilla, of a simple type.About the tip, where the papillzc are smaller and more closely set, there appear to be about thirty t o the square millimetre of surface.Posteriorly there are only half that number covcring the same area.Each papilla rests upon one or morc papillnrp upgrowths of the mucosa, and, at a short distance from its basc, breaks up into a varying number of very long, slender, recurvctl secondary papilla3 or processes.T h e number of these processcs varies greatly even in the same region.Thcre arc scldom less than ten, and T have seen more than fifty.The average numher appears to vary f m m sisteen to twcnty.Thc frce portion