REPORT OF THE SECRETARY. 15 



North American Horpctolouy, uiulertjiketi some years ago, at the re- 

 quest of the Institution. The materials which have been accumulating 

 in the National Museum offer great advantages for the investigation of 

 the anatomical structure, variation of specific cliaracters, and geo- 

 graphical distribution of animals. These subjects are especially eluci- 

 dated by the study of batrachians and reptiles, since these animals are 

 especially susceptible to effects from physical influences, and are una- 

 ble, like birds and mammals, to escape these by extended migrations. 

 Their habitats, therefore, express the simplest relations of life to the spe- 

 cial conditions under which it exists. The great number of specimens 

 in the National Museum enables the investigator to discover the range 

 of variations of a given species, and to reduce to the rank of varieties 

 many which have been supposed to be distinct species — the definition 

 of species being siuiply a number of individuals having physical pecu- 

 liarities belonging to them alone, and at the same time found in all. 

 Nothing is more diflicult than to divide the flora or fauna of the world 

 into distinct species, having the above characteristics, since, passing 

 from one locality to another of varying physical conditions, the varia- 

 tions in form and character are so gradual that it is almost impossible 

 to say where the line of demarkation shall be placed. 



In the investigation of cold-blooded North American vertebrata. Pro- 

 fessor Cope has found that many which have been regarded as se[>arate 

 species are merely geographical varieties. Bulletin No. 1 is divided 

 into three parts. 



Part I consists of an arrangement of the families and higher divi- 

 sions of the batrachia and reptilia provisionally adopted by the Insti- 

 tution. 



Part II is a check-list of the species of batrachia and reptilia of the 

 nearctic or North American realm. 



Part III relates to the geographical distribution of the vertebrata of 

 the nearctic realm with especial reference to the batrachia and reptilia, 

 and is divided into eleven sections. 



Life in different regions of the earth presents marked peculiarities, 

 depending in a great measure upon the geographical and topographical 

 relations of the continents. The districts thus marked out are the Aus- 

 tralian, the neotropical, the nearctic, or North American, the Ethiopian, 

 the PaUeological, and the Palajartic, and to these the name of "realms" 

 has been given. The total number of species of vertebrata found in the 

 North American realm is 2,L*49, which is below the truth, since many of 

 the fishes, both of the ocean and of the fresh waters, remain undescribed. 

 It is more difficult to give the number of species of the inferior divis- 

 ions of the animal kingdom. It is stated that 8,000 species of cole- 

 opterous insects have been discovered in the same region, and that this 

 is probably about two-thirds of the whole. Probably 50,000 is below 

 the mark as an estimate of the number of species of insects. In relation 

 to other realms, several species of vertebrata are common to our north- 



