302 THE SALAMANDER 



by comparison, that the Harderian and lacrimal glands have arisen 

 by differentiation from a common glandular mass. 



The naso-lacrimal duct runs from the anterior corner of the eye to 

 the nasal cavity passing beneath the pre-frontal bone in so doing. 



3. The Eyelids. 



The upper eyelid is the larger and is movable, as it is in the whole 

 family Salamandridae. The lower lid, according to Johnson, is prob- 

 ably homologous with the memhrana nictitans of higher vertebrates, 

 the true lower lid of these animals arising as a cutaneous fold external 

 to it, only a slight trace of this fold being detectable in the Sala- 

 mander. Both upper and lower lids are moved by means of a tendon 

 attached to the M.. retractor bulhi and they are therefore closed 

 synchronously with the retraction of the eye-ball (cf. p. 51). In 

 addition to this mechanism there are a few smooth muscle elements 

 in the upper eyelid so that it is apparently capable of some independent 

 movement. 



III. THE NOSE 



1. General. 



The olfactory passages of the Salamander are relatively large 

 chambers situated within the nasal capsules. With the exception of 

 a small area around the external openings they are completely pro- 

 tected by the skeleton. Two distinct regions are distinguishable in 

 each olfactory chamber, namely, the main chamber, or cavum nasi, 

 which is shaped like a flattened ovoid, from which protrudes a lateral 

 gutter-like diverticulum — the sinus lateralis nasi. Into this lateral 

 gutter the ductus naso-lacrimalis opens, while the external narial 

 opening is situated just mesial to its anterior end. The sinus lateralis 

 nasi is lined by ciliated epithelium, but not the main cavum nasi. 



2. Jacobson's Organ. 



In 1895 Seydel suggested that Jacobsons organ occurred in the 

 sinus lateralis, and named the gland lying just mesial to it, beneath 

 the cavum nasi, Jacobsons gland. In 1898 Mihalkovics opposed this 

 view on the ground that, in all other vertebrates which possess a 

 Jacobson's organ (including the Frog), this structure is found mesial 

 to the posterior nares and not lateral to them. He therefore concludes 

 that a true Jacobson's organ is absent in Salamandra, but agrees that 

 the sinus lateralis nasi — his recessus maxillaris — has a similar function, 

 namely that of testing the expired current, and he therefore regards 



