Coues.] 78 [May 19, 



May 19, 1869. 



The President in the chair. Twenty-three members present. 



Dr. Jeffries Wyman exhibited the head of a crocodile, C. 

 acutus, obtained in the Miami River, as it enters Key Bis- 

 cayne Bay, Florida. This was presented to him by William 

 H. Hunt, Esq., of Miami, and was the second that had been 

 shot at that place. The existence of a true crocodile within 

 the limits of the United States has not been previously 

 recognized, though the species just mentioned has long been 

 known in Cuba, San Domingo and South America. 



The following paper was presented : — 



On a Chick with Supernumerary Legs. By Elliott 

 Coues, A. M., M. D. 



The anatomical peculiarities involved in the freak of nature I am 

 about to describe, are sufficiently remarkable to render this monstrous 

 chick something more than an object of vulgar curiosity, and appear 

 quite worthy of being placed on record. Although four-legged 

 chicks, like double-headed calves and pigs, are not of very rare occur- 

 rence, comparatively speaking, this instance of monstrosity by redun- 

 dancy is unique, so far as I am aware, in the extent to which nature 

 has made sport of her laws for the development of limbs, and in the 

 kind and degree of asymmetry thereby produced. 



Regarding the development of supernumerary limbs, or parts of 

 limbs (the latter involving the production merely of redundant seg- 

 ments), two conditions have been so generally observed to obtain, 

 that they may fairly be held expressive of a certain kind of law to 

 which even these seemingly pure freaks are subjected. The first is 

 the degree of constraint imposed by the fundamental law of bilateral 

 symmetry, in obedience to which accessory or redundant limbs are 

 prone to make their appearance in pairs, opposite each other, on 

 either side of the body, so that the monster remains symmetrical, as 

 far as bilaterality is concerned. Two-headed creatures, in particular, 

 rarely, if ever, show departure from this condition. The second is, 

 that liability or tendency to reduplication of segments of limbs in- 

 creases from the proximal to the distal extremity of a member, pari 



