1895 | NEW YORK ACADEMY OF SCIENCES. 245 
In connection with the above-described variability in the 
position of the cloacal aperture it may be well to refer to the 
observation of Mary H. Hinckley (‘‘ Note on the development 
of Rana sylvatica, Leconte,’’ Proc. Boston Soc. Nat. Hist. XXII., 
1882, pp. 85-95), that among tadpoles of R, sylvatica and Rf. hale- 
cina (= R. virescens) 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 Alyles, Bombinator and Discoglossus, 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, asin Amphi- 
oxus, 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 FR. clamata. 
Cotumpia Cottecre, May 26, 1893. 
* This is the normal condition in Dactylethra 
