THE DRAMA OF LIFE 35 



ous or by being like ants. But as we have experimental 

 proof in a few analogous cases, it seems quite sound Biology 

 to say that these little Mantises probably get on very 

 much better because they have added to the usual incon- 

 spicuousness of their kind, the additional advantage of 

 being like ants when they are young. For by the time 

 they had attained a length of seven millimetres, they had 

 lost their ant-like look. 



Another ' device ' is that of masking, where the creature 

 disguises its real nature by covering itself with foreign 

 bodies. It is difficult to draw the line between extrinsic 

 armour and disguise. Thus the larval caddis-insects in 

 the streams cover themselves with minute pebbles or with 

 pieces of plant-stem and the like ; and this is probably in 

 the main a protection, not a mask. When we pass to 

 crabs covering themselves with sea- weed, or with sponge, 

 or with hydroids, or with part of a sea-squirt's tunic, we 

 have to do with something nearer masking. 



Zoologists are well aware that the little crabs of the 

 genus Cryptodromia are in the habit of masking themselves 

 with pieces of sponge or ascidian or the like. R. P. Cowles 

 has recently watched the whole process of sponge-cutting. 

 The naked crab (Cryptodromia tuberculata, in the Philip- 

 pines) cuts a groove on an encrusting grayish sponge, 

 works its way under it, and dislodges it. In a short time 

 the ragged edges of the sponge shield grow smooth and 

 neat. The cutting is done with the forceps, but the dis- 

 lodged piece is caught hold of and carried by the last pair 

 of legs. 



' It is a surprise to the collector when, on turning over a 

 rock covered with large and small patches, he sees some of 



