388 HARRIS IIAWTIIORXE WILDER ON 



groups, which are partially or Avhollj subterranean in their habits and thus modified in 

 various degrees to conform to this environment. Proteus is an inhabitant of certain 

 caves in Austria, and shows, among other troglodytic characters, reduction of ejes, loss of 

 pigment, and a pronounced attenuation of bod}^ and limb, the latter combined with a loss 

 of toes. These aberrant characteristics are still more marked in the recently discovered 

 Typhlomolge, which occurs in a subterranean river in the state of Texas. The third and 

 last member of the group, Necturus, occurs in the Great Lakes and other open waters, 

 and, corresponding to its freer life, shows the least modification. It remains by day 

 beneath stones or in subterranean burrows constructed by itself in the mud, and becomes 

 active at night, swimming through the water in search of prey. Its body and legs are 

 robust, and do not show the slender proportions seen in Proteus and Typhlomolge. Its 

 eyes, though small, are functional, and it is well pigmented, especially above. It is thus 

 at the same time a representative of the lowest group of Urodeles, and one not extremely 

 modified. 



The genus Necturus is exclusively North American and includes but one common 

 species, iV. maculatus Raf., although the series of synonyms, as well as some variability of 

 marking, have combined to give the general impression that there is a large number. 



Aside from N. maculatus Raf., Cope enumerates a second species, N. punc-tatus 

 GibbeS; of rare occurrence and found only in the waters of North and South Carolina. 



Necturus maculatus, the subject of this memoir, is a widely chstributed form and 

 occurs in abundance in the Great Lakes and their tributaries, and throughout the entire 

 Mississippi valley, as well as in many of the river systems of the Atlantic slope, and those 

 flowing into the Gulf of Mexico. Its abundance and extensive distribution have led the 

 United States government to conduct experiments relative to its introduction as a " food 

 fish," thus far with satisfactory results. In form and appearance it is similar to that of a 

 larval salamandi'id, and is subcylindrical, body slightly and head markedly depressed, 

 with three large and bushy external gills upon each side, ha\iug two gill slits between 

 them, and with four decidedly robust legs, each witli four toes. The tail, which does not 

 exceed half the length of the body, is compressed and surrounded dorsally, caudally, and 

 ventrally by a caudal fin, rounded in outline at the tip. Sexually mature adults seem to 

 be fairly constant in size, vai'ying in total length between about 27 cm. and 34 cm. 



The color markings of the integument are due to scattered pigment cells, the varia- 

 tions in the frequency and size of wliich result in the formation of all possible shades 

 between no color at all and dense black spots. As these cells are very large, and in most 

 places evident to the unaided eye, the principle is seen upon close inspection to be similar 

 to that of a modern half tone illustration, which a careful scrutiny resolves into a series of 

 black dots, although in the latter case the darker shades are due to increased size, and in 



