PUPIL SHAPES AND THEIR MEANING 



223 



zontal slit. It has this form for a few hours, at least, after the animal is 

 released from its mud-ball or aestivational cocoon. Eventually, however, 

 it rounds up and thereafter remains circular in all illuminations. Another 

 lungfish, Lepidosiren, has a small circular pupil which never changes; but 

 this fish has been claimed to have photomechanical changes in the retina. 

 Among the amphibians, the salamanders and caecilians all have round 

 pupils suited to their secretive and fossorial habits. Most anurans have 



a b c d efqhijk 



Fig. 87 — Shape of the contracted pupil in different amphibians. 



(All are circular when dilated. From various sources; right eyes; not to same scale). 



a, urodeles and aquatic anurans (Pipidje et al). b, most anurans. c, Hyperlius horstockH. 

 d, Polypedates reinwardti. e, Corythomcintis greeningi, Aparasphenodon hrunoi, and 

 Trachycephalus nigromaculatus. i, several anurans (see text), g, Scaphiopus and Phryn- 

 omerus. h, Hyla vasta. i, Bombina. ], Pelobates fuscus. k, Calyptocephalus quoyi. 



Fig. 88 — The gecko pupil. 



a, eye of a gecko in diffuse daylight, x 5. After Beer, b, c, d, stages in the contraction of 

 the pupil of the right eye of Tarentola mauretanica. After Lasker. e, iris musculature 

 of T. mauretanica (combined from two figures of Lasker). Sphincter fibers suggested by 

 solid lines, dilatator fibers by broken lines. Note that some sphincter traas surround the 

 pupil concentrically and others eccentrically, while still others have a closed circuit in either 

 the nasal or the temporal half of the iris. 



horizontal, broadly oval pupils. The rigidly nocturnal spade-foot toads 

 {Scaphiopus) , and the brevicipitid genus Phrynomerus also, have an 

 approach to the vertical slit in their beautiful lozenge-shaped pupils. The 

 vertical slit occurs in quite a number of nocturnal anurans — in Alytes 

 obstetricans, several criine toads, Lymnomedusa, Phyllomedusa and sev- 

 eral other bylines, some polypedatids, and Hypopachus. The Javanese 

 flying-frog, Polypedates reinwardti, has a slender horizontal slit, while 



