ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 247 



helps to support the caudal part of the patagiuru. It has been described 

 as tendinous, cartilaginous, and osseous ; it has been regarded as part 

 of the calcanenm, and otherwise interpreted. The authors find that in 

 young bats it is independent of the calcaneum. In the course of time 

 its axis ossifies at the expense of cartilaginous cells, and its proximal 

 end is united by amphi -arthrosis to the internal surface of the calcaneum. 



Respiration in Amphibians.* — H. L. Brunner has studied the 

 mechanism of pulmonary respiration in Amphibians with gill -clefts. 

 It is a force-pump mechanism as in higher Amphibians. In Necturus and 

 Proteus and the larvae of higher lung-bearing Urodeles, a median 

 choanal valve prevents the escape of the air from the mouth through the 

 nasal cavity ; in Siren there is this median valve and there is a posterior 

 one, enclosing the antorbital cartilage, by means of which the choana 

 can be opened ; in Amphinma there are smooth muscles for opening and 

 closing the nasal vestibule, and there is a complicated choanal mechanism, 

 which includes the antorbital cartilage and two striated muscles ; in 

 Gryptobranchus the choana is closed by the hyoid arch, and respiration, 

 both bucco-pharyngeal and pulmonary, is similar to that in A mphiuma. 

 It may be said that Necturus and Proteus are slightly modified permanent 

 larvae, that Siren is a modified larva whose choanal mechanism has been 

 brought under muscular control ; that Cryptobranchiata are much 

 modified arrested larvae with the essential parts of the aquatic mechanism 

 except gills, and also with the pulmonary mechanism of the higher 

 Urodeles. 



Olfactory Sense in Amphibians.f — H. L. Brunner finds that the 

 usual medium of smell is the same as that used in bucco-pharyngeal (or 

 branchial) respiration, which is renewed by regular oscillations of the 

 floor of the mouth. Under ordinary conditions the intermittent pul- 

 monary respiration has little or no value for olfactory purposes. The 

 olfactory medium may be air or water. In adults the olfactory organ is 

 more highly developed in air-smellers than in water-smellers. 



There are two types of olfactory (respiratory) mechanism ; (a) in 

 the first type the respiratory medium passes freely inward through the 

 nasal cavity to the mouth, but its return is prevented by a valve ; (b) in 

 the second type the respiratory mechanism is wholly under muscular 

 control, and the olfactory medium passes freely in and out through the 

 nasal cavity. 



Thus Brunner distinguishes (a) monosmatic forms (single smellers) 

 including Necturus and the larvae of Ambly stoma and Rana, in which 

 the olfactory organ is used to test only the external medium, from 

 (b) diosmatic forms (double smellers) including Siren, Cryptobranchus, 

 Amphiuma, larvae of lungless salamanders, and the adult stage of higher 

 Amphibians, in which ingoing and outgoing currents bear odorous matter 

 to the olfactory organ, which is accordingly used to test both the 

 external medium and the contents of the oval cavity. 



In. single smellers, Jacobson's organ is wanting, and the olfactory 



* Morphol. Jahrb., xlviii. (1914) pp. 63-82 (11 figs.). 

 t Morphol. Jahrb., xlviii. (1914) pp. 157-65. 



