THE AMERICAN NATURALIST. [Vol. XXXVII. 



gastrosteges are black with a little white on the posterior edges ; 

 urosteges mostly black, with inner edges white ; head mottled, 

 light and dark brown ; lower edge of upper labials pale gray. 



The colors of sipedon do not undergo a very marked change 

 during a few months in alcohol or formalin, simply becoming 

 more dull, though after the lapse of years they fade, especially 

 if exposed to the light. The colors of erythrogaster, however, 

 are completely changed in either formalin or alcohol, the black 

 tending to become bister or clove brown and the whole under 

 surface becoming pale cream color, with faint indications of 

 slate on the anterior edges of the gastrosteges. The twenty- 

 seven specimens of erythrogaster collected about Olivet showed 

 practically no variation in color, except that a few had the mid- 

 ventral line a somewhat deeper shade of rufous. In no case 

 was there the slightest evidence of markings on the back, or 

 of spots on the belly. The sixty-three specimens of sipedon, 

 on the other hand, show a very wide range of variation, not 

 only in the distinctness of the markings and in the amount of 

 brown and black on the ventral surface, but also in the shade 

 of the ground color, both dorsally and ventrally. The middle 

 of the ventral surface is often marked with an ill-defined longi- 

 tudinal area of yellowish, sometimes almost reddish yellow. 

 Just before the shedding of the skin, the black of erythrogaster 

 becomes very dull, and the ventral side a dull, almost salmon, 

 red, quite different from the normal shade. In captivity this 

 stage may last two or three weeks, but in freedom it is probably 

 passed through more rapidly. In sipedon the casting of the 

 skin causes a preliminary obscuring of the dorsal markings, so 

 that in cases where they are naturally faint they may be 

 apparently wanting. 



However much specimens of sipedon varied from normal, 

 none of those examined showed the slightest approach to 

 erythrogaster, and it is very difficult to see how the coloration 

 of the latter could ever have gradually developed from that of 

 the former. While still seeking a solution of this puzzle, four 

 specimens of Natrix from the United States National Museum 

 very kindly loaned to me by Dr. Stejneger. Of these I 



shall have more to say later. Suffice i 



say here that they 



