294 I N A G U A 



Nor is this all, for nature, not content to offer all these wonders 

 in one creature, has ordained that they may swim, not only 

 forward like all other creatures of the sea, but backward! They 

 can swim forward and sideways, too, but the normal mode is 

 stem foremost. 



The quill of these mobile fountain pens is the remnant of 

 the shells of their prehistoric ancestors, and it persists, like our 

 vermiform appendix, as a useless but telltale evidence of former 

 usage. The quill, reduced in the octopi to two chitinous rods, 

 and in the squid to a long narrow fluted pen, remarkably re- 

 sembling an old fashioned quill, is buried deep within the tissue. 

 In a sense, the octopi and squids are shellfish which have sur- 

 rounded their shells. 



It is in the ink of these cephalopods that we are confronted 

 with a true paradox. This ink, basis of the familiar India ink, is 

 utilized for two diametrically opposite purposes. It is intended 

 to provide concealment and, diversely, to enable the animal to 

 keep in touch with its fellows. When there is fear of an attack 

 by enemies, the ink is expelled into the water to form a "smoke 

 screen" behind which the cephalopod flees to shelter. Thus 

 the modern military technique of employing the smoke screen 

 to conceal retreating movements was conceived by the cephalo- 

 pods as early as the Jurassic, as is proved by a beautifully pre- 

 served fossil of that period which shows the ink bag promi- 

 nently Hmned in the highly compressed tissue impression of a 

 squid. However, when night closes down on the water shroud- 

 ing the blue vastness of the deeps in impenetrable gloom it is 

 by means of this same ink that the members of a school of squids 

 are able to keep in contact with one another. It is beheved that 

 the ink is extruded in very small quantities and is picked up by 

 unusually sensitive olfactory organs. The more solitary octopi 

 use it in much the same manner to locate their mates. 



I had no idea of the efficiency of this inky fluid until my 



