128 How Animals Changed 



portionally well developed. Sensory hairs and gustatory and olfac- 

 tory organs change their character completely when arthropods 

 change their habitat from water to land (Marcus, 1911; Harms, 

 1929) . Odors are important in the daily life of many land crus- 

 taceans (Borradaile, 1903; Harms, 1929) and constitute the basis 

 for the social life of insects (Kennedy, 1927a) . Some polychaete 

 worms which live on land have sense organs which resemble those of 

 arthropods (Harms, 1929) . 



The eyes of fishes which live on land have been much studied 

 (Beer, 1894; Baumeister, 1913; Hess, 1913; Harms, 1914, 1929; 

 Weve, 1922; Karsten, 1923; SchreitmuUer 6C Relinghaus, 1926). 

 The climbing perch (Anabas) has eyes like aquatic fishes, and is 

 myopic in water and on land. The beach-skipping gobies belonging 

 to the genus Periophthalmus, however, differ from other fishes in 

 being hypermetropic and in other respects are adapted for life on 

 land. In common with other fishes which live in mud these gobies 

 have a liquid-filled chamber in front of the cornea for protection. 

 They are unlike other fishes in having to accommodate their eyes 

 for near vision, in having the eyes protuberant and quite movable, 

 and in possessing a considerable degree of binocular vision. A 

 beach-skipper can see a termite clearly at a distance of two to three 

 meters. 



Amphibia furnish favorable material for the study of changes in 

 sense organs with the assumption of terrestrial life, because many of 

 them spend part of their life on land and part in water. Matthes 

 (1927) has investigated the olfactory organs of the European newt 

 (Triturus) . He finds that when a newt is changed from water to 

 land there is a temporary loss of ability to smell, but recovery takes 

 place after three or four days. The nasal epithelia are quite differ- 

 ent in land and water newts. The olfactory hairs in the former are 

 five times as long as those in the latter. If a terrestrial newt is 

 replaced in water, its olfactory hairs soon shorten. 



