1^6 AVERS. [Vol. VI. 



They recognize three forms of this kind of sense organ, which 

 they designate as 



1. Sinnesurzelle = Stiftchenzelle. 



2. Becherorgan. 



3. Geschmacksknospe. 



In this account of the surface sense organs of Ichthyophis, 

 the Sarasin brothers (1890, 248) describe a second kind of organ 

 found by them, which they call an "Accessory ear" or " Flask- 

 shaped " sense organ. The body of such a sense organ is more 

 or less flask-shaped with a central lumen which has to a greater 

 or less degree the shape of the organ. Within this cavity freely 

 suspended, perhaps supported on the ends of the sensory hairs, 

 is a club-shaped, highly refractive body, which is largest at its 

 inner end and gradually tapers outward, ending just at the level 

 of the surface of the skin, never projecting beyond it. This 

 body the authors call the "keulenformiger Korper," and suppose 

 it to be composed of a homogeneous and coagulable secretion. 



The walls of the organ are divisible into two very distinct 

 parts, an upper and outer or communicating tubular portion, 

 and an inner or basal sensory portion. The walls of the former 

 are composed of ordinary epithelial cells, while the latter is 

 composed of the thickened sensory epithelium — some of the 

 cells of which are hair bearing. These sense cells are probably 

 derived from a division and aggregation of primitively isolated 

 nerve end cells (Sinnesurzellen), which by the development of 

 surrounding and supporting cells produces the taste bud or 

 associated sense organ. 



The innermost layer of cells is composed of pear-shaped sense 

 cells, each of which bears a distinct, stiff, refractive hair which 

 runs to the surface of the club-shaped mass and inserts in it. 

 Consequently the club rests upon the points of the hairs of the 

 sensory cells. A boundary between hair and sense cells the 

 Sarasin brothers were unable to find. 



The ganglion below the sense organ develops only after the 

 larva enters the water. The function of these organs is doubt- 

 less that of hearing. The little club which rests on the hairs 

 they designate the auditory club. The organ itself is the acces- 

 sory ear of the Ichthyophis larva. 



In this organ we have represented all the essential parts of 



