174 THE STUDY OF ANIMAL LIFE CHAP. 



conceived purpose. Much of man's activity is intelli- 

 gent behaviour, much is intelligent behaviour that has 

 become habitual, but in either case there may be, if 

 occasion arise, an instantaneous transition to the higher 

 level of rational conduct. 



12. Artistic Skill. Most of the Foraminifcra form 

 shells of lime, which are often of great beauty.. There 

 are others which make shells of extrinsic pa rticles selected 

 from the surroundings and effectively built together. 

 We are here contemplating the dawn of art. In their 

 interesting studies on arenaceous Foraminifera Messrs. 

 E. Heron-Allen and A. Earland have disclosed a remark- 

 able series of facts. One species of Foraminifer (though 

 it is difficult to say what species means here) will use 

 nothing for its encasement save intact sponge-spicules, 

 a second will use only grains of quartz, and a third flakes 

 of mica. Quite extraordinary is a species of Technitella 

 (i.e. " little workman ") w r hich makes its test of delicate 

 Echinoderm plates, and, having no definite oral aper- 

 ture, sends its threads of protoplasm through the pores 

 which the plates possess. Very striking also is a species 

 of Reophax which forms a fragile many-chambered tube, 

 built of infinitesimally small flakes of mica, joined at 

 their extreme margins by chitinous material. When the 

 Protozoon is living, this delicate covering is pliable like 

 chain armour. The striking facts are individuality of 

 architecture and the apparent selection of particular 

 kinds of material from amid an embarrassing multitude 

 of alternatives. Experiment is needed to show how far 

 this is obligatory, how far facultative. 



Very interesting, furthermore, is the effective way in 

 which some of these shell-builders use their materials. 

 In a species of Technitella the whole shell- wall consists of 

 two distinct layers of sponge-spicules, " giving as close 

 an approximation to the woof and warp of a textile 

 fabric as is possible with a rigid non-flexible material 

 such as sponge-spicules." In some forms the sponge- 

 spicules are arranged protectively, in others there are 

 long projecting rods, like " catamaran spars," which 

 support the shell on the surface of the ooze. Two or 



