INTRODUCTION. 67 



forms, as those represented in our tliird wood-cut. 

 In general, its cavity is without any partitions, as 



akeady stated ; but in some members of the genera 

 Diodon and Tetrodon^ tribes remarkable for their 

 uncouth globular form and prickly surface — as well 

 as in the genus Silurusy and in the sword-fishes 

 (Xiphias)^ it is sub-divided in the manner of the 

 lungs of reptiles, so that its interior has a cancel- 

 lated, or honey-comb appearance. This coiTCspond- 

 ence of the air-bladder of fishes and the membra- 

 neous lun^s of reptiles, is a powerful argument in 

 favour of the doctrine of those who represent all 



