602 ni-. HARKIS 11. WILDER, 



of Siren. To effect this action, the dorsal half of the tube 

 acts as a dilatator and the ventral half as a cous trie tor 

 of the laryngeal lumen, 

 e) The sphincter action has gradually retreated before that of 

 the more practical lever, until it is retained only in a certain 

 region {Siren\ or has disappeared entirely (higher animals). 



III. The anatomical relations of the nasal region have been worked 

 out in detail and are shown in fig, 11, and in the sections fig. 12, 

 A, B, C. The principal points of interest which may be claimed as 

 new are the following: 



a) The nasal capsule forms merely a roof for the protection 

 of the sense organ beneath. It is oval in shape with a lateral 

 wing and exhibits a large irregular foramen near the centre. 

 The anterior inner corner forms a sheath for the protection 

 of several important nerves. 



b) The nasal cavity consists of a main and an accessory 

 cavity. This latter lies medially and inferior to the other, 

 communicates posteriorly with the main cavity and ends an- 

 teriorly in a double blind sack. A transverse section taken 

 through the region of this double sack (fig. 12 C) displays 

 three nasal cavities, separated from one another. 



c) A well - developed intermaxillary space is present. It 

 shows, however, a retrogression from an originally larger 

 cavity, being partly filled up with loose connective tissue. 



d) Intermaxillary glands occur and lie in two latn-al 

 groups mostly at the sides of the intermaxillary space, the 

 position they occupy in the larval form of Amblystoma wcis- 

 manni. 



A few remains of glands are seen to occupy the intermaxillary 

 space itself. 



IV. With regard to the phy loge ne tie relations of Siren, 

 I am fully convinced that it has once possessed a terrestrial existence 

 and been driven back to an aquatic life during the struggle for 

 existence, similarly to the case of the Axolotl. Like the Axolotl it 

 may be considered a larval form of a Salamandrid, but unlike the 

 Axolotl , which has simply repressed the later stages and represents 

 still a fairly typical larva , the Siren - form has been modified by 

 the infiuence of external conditions during a much longer period of 

 time, and thus no longer represents a simple larva but adegenerate 

 and nj odified one, 



