ix ANIMAL BEHAVIOUR 175 



three individuals may be united in this way by sharing 

 spars, ' the association offering greater resistance to the 

 mud than a single individual can attain." Gaps in the 

 wall of the shell of a species of Psammosphsera are filled 

 in with fragments of spicules " carefully selected for 

 length so as exactly to fill the spaces that are to form 

 the walls of the test, an awkward triangular space being 

 frequently filled in with a truncated triaxial spicule." 

 Very instructive is the story of Marsipella spiralis which 

 arranges its borrowed sponge-spicules in a left-handed 

 spiral and embeds them firmly in cement, thus improv- 

 ing on the shell of its neighbour-species M. cylindrica, 

 which forms a long and exceedingly friable tube. Mr. 

 Heron-Allen compares M. tpiralis to the prehistoric 

 genius who invented string " it has clearly realised that 

 a twisted yarn is stronger than an untwisted wisp of 

 fibre." This phraseology is too anthropomorphic, but 

 it probably expresses a great truth, that all through the 

 animal kingdom there is organic skill, associated with 

 different degrees of awareness. One of the wavs in which 



u 



those psycho-physical individualities which we call organ- 

 isms express themselves is in the skilful use of materials. 



Among tube-building worms, tailor-crabs, hive-bees, 

 wasps, spiders, and so on up to nest-building birds, we 

 see individual, specific, effective, adaptive, and beautiful 

 utilisation of materials, and often a remarkable triumph 

 over the difficulties which they involve. Just as we 

 may distinguish rational skill, intelligent skill, and in- 

 stinctive skill, so there may be,, in the arenaceous 

 Foraminifera referred to, an organic skill, when the simple 

 individuality, pulling itself together, acts as a unity and 

 then perhaps feels itself as one. For it is not fantastic 

 to suppose that in such critical moments of endeavour 

 and adventure consciousness first found, and still finds, 

 its simplest glimmering expression. Perhaps we are 

 nearer the truth in supposing that Technitella says to 

 itself in some quiet way of its own " Anch' io sono pittore," 

 than in supposing that its remarkable artifice can be 

 exhaustively described in terms of surface-tension. 



13. Spontaneity. We cannot evade the difficult ques- 



