340 VICTOR E. SHELFORD. 



(Derocrania, Horn, '99, pp. 228-230), for depositing eggs 

 in twigs (R. Shelford, '07). Apparently several of these types 

 may occur, one above the other, in one locality, or at least 

 at different levels in adjoining localities (R. Shelford, '02, pp. 

 233-234). 



Among the Orthoptera we find forms adapted to burrow beneath 

 the soil, others which live at the surface of the soil having ovi- 

 positors adapted to deposit eggs in soil, feet adapted to life on 

 soil, etc. Those that live on the shrubs are adapted to walk on 

 vegetation, and to deposit eggs in plant tissues (Morse, '04). 

 Motile aquatic animals are adapted to burrow into the bottom, 

 to cling onto the bottom, to cling on the vegetation or zoophytes, 

 or to swim about. Feeding adaptations in the fishes are to feed 

 in the open water, in the vegetation, or on the bottom, each of 

 which is a relation to stratum or matters comparable to strata. 



Mammals are adapted to aquatic, subterranean, cursorial 

 life. By way of further example, let us take the pocket gophers 

 which occur (Merriam, 95) in the subterranean stratum of all the 

 great steppes, deserts, and dry and moist forests of the United 

 States and Mexico, apparently from the most arid deserts to the 

 moistest tropical and subtropical forests. Adaptation limits 

 their relations only to stratum. Again cursorial mammals, with 

 all possible numbers of toes, are found in all of the climates of the 

 world, in the forests, steppes, and deserts, arctic and tropic, all 

 being adapted to the ground stratum. The arboreal types are 

 likewise widely distributed. Arboreal monkeys, for example, 

 occur from the snow covered pines of the Himalayas (Heilprin, 

 '87) to the moist unchanging forests of the Amazon, all being 

 adapted to the tree stratum. In many taxonomic groups, such 

 as families and even genera, we find structural characters which 

 seem fitted to various levels of habitats, but which do not limit 

 the animal to any particular ecological types of plants growing in 

 any particular set of physical conditions. Neither do they, in 

 many cases, seriously limit its mode of activity. Adaptations 

 to stratum appear in many cases to be quite elementary, occurring 

 within genera, while other adaptations such as those for food 

 getting, belong to larger taxonomic groups such as orders and 

 suborders. Those of higher order are however never of primary 



