2 F. Tnckerman, 



presence or absence of sense-organs, this tongue is interesting from 

 a long wonnlike process, some 28 mm. in length, which it bears near 

 its anterior extremity. The process is fixed near the middle in a 

 groove of the organ, and possesses an outer and inner free portion. 

 The outer portion, longer and stouter than the inner, projects for some 

 distance beyond the tip of the tongue. It is quite possible, as Dr. Baur 

 suggests, that this appendage is a modified or greatly hypertrophied 

 simple papilla, there being nothing in its structure apparently to con- 

 trovert such a view. The process is freely movable, and doubtless 

 serves the purpose of enabling the animal to attract its prey. 



Testudo tabulata. 



Before passing to the consideration of the histological details, I 

 will describe very briefly the form and general appearance of the 

 tongue of this chelonian. The organ, except at the extremities, is 

 fii'mly united to the floor of the mouth. It measures 17 mm. in length, 

 its greatest transverse diameter is 15.5 mm., and at its thickest part 

 it measures 7 mm. The anterior end projects but slightly, there being 

 below the tip only about a square millimetre of free surface. The 

 back part of the tongue is distinctly bilobed. The dorsum is beset 

 with numerous elongated papillae, the points of which are directed 

 backwards. 



Microscopie Appearance. — The whole upper surface of the tongue 

 is papillate. The papillae vary somewhat in shape, but they are for 

 the most part long and narrow, and terminate in a rounded or pointed 

 extremity. At the sides of the organ they are smaller and more 

 uniform in appearance, but less completely differentiated, and their 

 summits are more or less flattened in this region. The papillae are 

 protected by a fairly uniform layer of epithelium, that investing the 

 upper surface being slightly thicker than that covering the lateral 

 area, and measuring on the average 0.125 mm. in thickness. The 

 superficial layer is very thin and, in places, is partly cornified. Under- 

 lying this is a thicker layer, consisting above of nucleated fusiform or 

 ovoidal cells, and below of cells polyhedral or spheroidal in shape. 

 'Hk' basal layei' is composed of cells moie or less elongated, but true 



