350 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



optic vesicle is formed. From the front of this arise new 

 wall-like growths, forming an anterior or second optic ves- 

 icle, cornea, and iris. The lens, curiously enough, is se- 

 creted from the cells of the anterior wall of the primary op- 

 tic vesicle, and is quite free from cell-structure. It is a cu- 

 tlcular formation, such as the bristle of an annelid. The 

 cells of the posterior part of the primary optic vesicle be- 

 come modified, so as to form the two layers of retinal ele- 

 ments. It is important to observe that in Nautilus there is, 

 as Heusen described, no lens, and but one optic chamber. 

 In fact, Nautilus has exactly the arrangement in adult life 

 which is seen in the early condition of the eye of the cuttle- 

 fish, before the wall of the primitive optic vesicle has quite 

 closed in. The small hole thus left permanently in Nau- 

 tilus represents the pin-hole aperture in a camera obscura, 

 and gives a luminous image. 15 A, September 5, 1874, 

 31 a 



RESPIRATION IN THE AMPHIBIA. 



Modes of respiration of animals which are aquatic for a 

 part of their existence are much varied. As is well known, 

 the gills of larval salamanders are exposed, while those of 

 frogs, etc., are concealed within a sac-like covering of the 

 skin. The larvae of a South American tree-frog (Notodel- 

 phys ovifera, Weinl.) possesses bell-shaped membranes in 

 place of gills, over which the bronchial arteries and veins 

 ramify. They occupy a sac on the back of the parent, which 

 is formed by the involution of the ordinary integument. 

 The Cceciliai are snake-shaped batrachians, which are found 

 in all tropical regions. They have no limbs, and frequently 

 no tail. One species has been known to possess fissures on 

 the side of the neck in the larval state, which subserve res- 

 piration before the animal assumes terrestrial life. It is the 

 Epicrium glutinosum of Ceylon. Recently Professor Pe- 

 ters, of Berlin, announced the interesting fact that the large 

 Gcecilia compressicauda of Surinam is viviparous that the 

 young are born in the water, and that they do not possess 

 fissures, but external gills. These organs are flat, leaf-shaped 

 sacs, which rest against the sides, and are supplied with the 

 bronchial vessels. When the animal leaves the water, these 

 appendages drop off, leaving a scar. 



