1893] NEW YORK ACADEMY OF SCIENCES. 245 



In connectiou with the ubove-desciibed variability in the 

 position of the cloacal apei'tuie it may be well to refer to the 

 observation of Mary H. Hinckley (" Note on the clevelojnneut 

 of Pmhu xi/lvatico, Leconte," Proc. Boston Soc. Nat. Hist. XXII., 

 1882, pp. 85-95), that among tadpoles of li. io/lvalica and Ji. hak- 

 cina (= R. virescen.s) individuals are occasionally met with having 

 two branchial pores or spiracula situated on the right and left 

 sides of the body respectively*, the usual condition of course 

 being, to have only the left spiraculum persisting. As is well- 

 known, in the tadpoles of Ahj/e^, Bombinator and DiacogloHsnx, the 

 single spiraculum is placed in the mid-ventral line. 



The fact of the asymmetrical position of such apertures as 

 those spoken of above, to which may be added the olfactory pit 

 of Amphioxus which lies on the left side of the body, together 

 with the fact that as a rule their position on this or that side of 

 the body is remarkably constant, looks very much like an 

 acquired character which has been fixed by inheritance. It can 

 be no conceivable advantage to an animal to have, as in Amjilu- 

 iiXHS, for instance, the anus to the left rather than to the right of 

 the integumentary expansion which forms the caudal fin, but its 

 constant position on the left side becomes intelligible, if it is re- 

 garded as an acquired characteristic which has become inherited. 

 The same argument applies to the (somewhat less) constant 

 position, to the right of the middle line, of the cloacal aperture 

 in the tadpoles of It. clamala. 



Columbia College, jMay 26, 1893. 



This is the normal condition in DactyMlira 



