Dr. A. Giinther on a new Siluroid Fish from Ceylon. 47S 



that this liquid is contained in a little box, of which the anterior 

 and posterior surfaces are made of thin glass. 



The numbers which I have obtained in the same medium and 

 for the same individual are very close, which justifies our having 

 confidence in the results of experiments so delicate ; but, more- 

 over, as may be seen from the table which I give in my memoir, 

 the distances of distinct vision in the air and in water are always 

 very nearly the same. Fishes, therefore, as I have already said 

 from the consideration of the structure of the eye, see as well 

 in the air as in water. 



Hence, also, the vision of Amphibia finds a natural explana- 

 tion, as the visual organs of those animals resemble those of 

 Fishes. Nevertheless, as a confirmation of the theory, I have 

 subjected to the same experiments the eyes of some Batrachia ; 

 and in these also the distances of distinct vision in air and in 

 water are, so to speak, identical. I shall only remark, in con- 

 cluding this analysis, that, in the Amphibia, distinct vision, which 

 is necessarily very short in water in consequence of the imper- 

 fect transparency of that medium, must, on the contrary, be able 

 to extend itself in the air to very variable distances, which ne- 

 cessitates the existence of a faculty of accommodation ; and ac- 

 cordingly the presence of the ciliary muscle, the chief agent of 

 that faculty, has been recognized in their eyes. 



LX. — Description of a new Siluroid Fish from Ceylon» 

 By Dr. Albert Gunther. 



[Plate XV.] 

 A SMALL collection of freshwater fishes, made by the Rev. Ban- 

 croft Boake in Ceylon, and kindly submitted to my examination 

 by F. Layard, Esq., contained two Siluroid fishes of the genus 

 Arius, which are of great interest, inasmuch as they prove that 

 the peculiar habit which I have described in an American species, 

 A. fissus (Fish. v. p. 173), viz. the mode in which the parent fish 

 takes care of its progeny, is not confined to South-American spe- 

 cies, but exists also in the East-Indian ones. The mature ova are 

 of the same large size in all these fish ; and in all it is the male 

 which carries them in the spacious cavity of its mouth. Accord- 

 ing to Mr. Boake, who has published an account of the habits 

 of these fish, they are called Angaluwa. Three specimens were 

 in the collection, belonging, however, to two very distinct 

 species, new to science. Two of these, a male and a female, 

 14 inches long, are Arius Boakii, so named by Mr. W. Turner, 

 who also had received examples, and read an account of them 

 at the last meeting of the British Association. We may there- 



