96 SATl^JJDAY LECTURES. 



brought uiuler chaii^ed iiiiluciK-cs. Tlic Siredon form of 

 this hist is known by the rather un})r()UOunceable name of 

 Axolotl, or Awahgolotel as the Mexicans speak it, and the 

 mature form is Amblystoma mexicanum. 



It greatly resembles the species first mentioned, and since 

 this has been referred b}' different authors to three or four 

 difibrent genera and varies so as to have had at least half a 

 dozen specific names given to it, we may pretty safely as- 

 sume that the INIexican form is also but a well-marked va- 

 riety. Most re})tiles, and especially batrachians, vary much 

 in color, and have the power in greater or less degree of 

 simulating that of their surroundings. Tlie common tree- 

 toad is a familiar example ; so that the discussion about 

 species may sometimes be likened to the quarrel of the 

 knights who were looking on different sides of the same 

 shield. Before leaving the Siredon I desire to say, in justice 

 to the able and beloved director of this Museum, that 

 already in 1849, or long before their specific connection had 

 been established by experiment, he correctly inferred that 

 Siredon would prove to be the larva of Amblystoma. 



THE HOUSE-FLY. 



The most persistent companion of man is, perhaps, the 

 house-fly. It has followed him everywhere in his own con- 

 veyances, and is found, so far as we know, wherever civilized 

 man has established himself. Our American house-fl}^ was 

 described as a distinct species {Musca harpyia) by Harris, 

 but Packard found it, after critical comparisons, specifically 

 identical with the Linnaeali species. Already, with the 

 growing warmth of this beautiful spring month, the fly be- 

 gins to show its familiar form in our houses, and to inspire 

 the careful housekeeper with feelings anything but agreeable. 

 Whence comes it ? How has it passed the winter ? Such 

 questions are often asked. Let us answer them. Not all v/ho 

 have watched the fly poising or darting noiselessly and 

 gracefully in mid-air, or deftly making its toilet, have real- 

 ized that at one time it was a crawling maggot, as unlike its 

 perfect self as two things well can be. The eggs are about 



