112 LIFE : OUTLINES OF GENERAL BIOLOGY 



shells, clouds of midges and Mayflies, vast groves of corals and 

 zoophytes. The variety of form and habit is so great that it is not 

 sm prising to find every here and there some social acti\ity. Thus the 

 social note is struck when the Procession Caterpillars go on the march 

 in Indian tile, the liead of one touching the tail of its neighbour in 

 front. This makes for efliciency when the leader linds a patch of 

 moist soil into which they all burrow and undergo metamorphosis; 

 and it is no argument against the general efticiency that the file 

 should continue for days in futile circumambulation, as when Fabre 

 led the procession round his fountain edge, the head of the leader 

 touching thi- tail of the hindmost. It is characteristic of instinctive 

 bi-haviour that it loses its effectiveness when there is a departure 



R WA 



IG. 31. 



Female Paper Nautilus in its Swimming Position. A, one of the ordinary arms; 

 SH, exposed {portion of the shell; ICSH, enveloped portion of the shell; 

 HWA. right webbed shell-making arm; LWA. left webbed shell-making 

 arm; E, eye; F, funnel. From a si)ccimcn, contradicting most figures. 



from the ordinary routine. Hut our present point is that the march of 

 the Procession Caterpillars is a social beginning, and so also for the 

 common canopy of silk with which they invest themselves when 

 they are browsing on the branches of tlu> j)ine-trees. 



One of the most beautiful sights in the world, sometimes seen in 

 the Mediterranean, is a fleet of female Paper Nautili or Argonauts. 

 Each is seated in a delicate spiral shell, more of a cradle than a 

 house, and. looking backwards, each is driving itself forwards by 

 an outgush of water through a narrow funnel o|xning out of the 

 gill-chamlxT. They sometimes move slowly in long lines on the 

 surface of the sea, but that in itself is not more than gregariousness. 

 The slender social Ix'ginning is in the fact that one Argonaut is 

 sometimes linked to its neighbour in front by having one of its arms 

 resting on the other's shell, while it is itself in turn touched by a 

 neighbour from behind. 



