QO AVERS. [Vol. VI. 



The brothers Sarasin (1887, 248, II, 2, p. 46) describe a 

 mucous secretion which they found quite regularly in prepara- 

 tions of the sense organs of the Ichthyophis, which surrounded 

 and extended beyond the sensory hairs, was unstained by borax 

 carmine, and was undoubtedly excreted by the supporting cells, 

 since the sensory cells all ended in sensory hairs, which pre- 

 cluded the formation of an excretion. They were unable to 

 decide which of the supporting cells were concerned in the pro- 

 duction of the secretion, and expressed the opinion that they 

 all possessed limited secretory powers. The secretion thus 

 produced may form a tubular process projecting beyond the 

 sense organ and serving in a measure to protect it. This is 

 the equivalent of the so-called hyaline tube so often described 

 for fishes and larval amphibia by F. E. Schulze and others. 



It hardly admits of doubt that the auditory club described by 

 Sarasin brothers for the well-developed lateral sense organs 

 which they consider accessory auditory organs is either a prod- 

 uct of the sensory hairs alone, in which case it would be the 

 analogue of the cupulae, or of these and some additional sub- 

 stance. In any case it has nothing in common with the audi- 

 tory otoliths. 



As I shall show further on, the so-called supporting cells are 

 in part true mucous cells, and the hyaline tube is a product of 

 their genuine mucous secretion, its tubular form depending on 

 the absence of the secreting cehs from the centre of the sense 

 orgfan. This secretion bears the same relation to the sense 

 or^an that the mucous canals of Elasmobranchs do to the am- 

 pullas of Lorenzini, which lie at the bottom of canals, i.e. at 

 their proximal blind ends. 



The auditory club which these authors describe for the acces- 

 sory auditory organs of the trunk region of Ichthyophis is very 

 refractive, but is not a genuine otolith, since it lacks calcareous 

 matter, and it is further not a true cuticular structure, since it 

 swells in strong caustic potash and dissolves. They considered 

 it to be a hardened glandular secretion, the product of the gland 

 cells {i.e. supporting cells) of the organ, and functional as an 

 otohth. The structure readily falls out of its cavity in manipu- 

 lation so that sections are found without this structure. 



The test of their view that these lateral line organs were ac- 

 cessory ears the authors found in the study of the ear itself, and 



