94 WHAT IS LIFE 



conical mouth of each chamber projecting into 

 the cavity of the next, while forming the walls of 

 its chambers of ordinary sand grains rather loosely 

 held together, shapes the conical mouths of the 

 chambers by firmly cementing together the quartz 

 grains which border it." 



Well may the writer just quoted add the 

 remark : " There is nothing more wonderful in 

 nature than the building up of these elaborate and 

 symmetrical structures by mere jelly-specks, pre- 

 senting no traces whatever of that definite or- 

 ganisation which we are accustomed to regard as 

 necessary to the manifestations of conscious life." 



In this variety of construction and in this 

 choice of materials it is hard not to see purpose. 

 Arceiia However, a further example of the purposive actions 

 of these minute forms may be given before we 

 leave the matter. There is a foraminifer named 

 arcella which makes for itself a round concavo- 

 convex test. On the concave side there is a single 

 central round opening through which it is able to 

 protrude its pseudopodia. 



One may colloquially speak of this surface as 

 its front and the convex aspect as its back. Now 

 sometimes it will occur that arcella will tumble 

 over on to its convex back and in that position one 

 would suppose that it would be as powerless and 

 even more helpless than the beetle which one sees 



