172 



KNOWLEDGE. 



[August 1, 1899. 



It is all very well for mankind to agree to put the 

 sword into its scabbard and keep it there. In the case of 

 several crustaceans the following of this pacific example 

 would not be by any means easy. Crabs and lobsters, it 

 is true, do sometimes cast off their formidable cutting and 

 pinching chelfe of their own accord. But there is always 



Spirontocaris spinus (Sowerby). From Spence Bate. 



a faint suspicion that they do this after they have had 

 their fill of fighting, and when the mauled and battered 

 weapons have become no longer serviceable to their 

 owners. They speedily proceed to grow new ones, at first 

 small and weak, as if only for the look of the thing, but in 



Raptorial Claw of Squilla raphidea Fabrioius. M. A. S. 



coarse of time their armature comes out as good as ever, 

 or possibly a little improved. 



When we turn to the prawns, we find many of them 

 equipped in such a way as to put suppression of armaments 

 out of the question. You cannot sheathe a sword that is 

 an immovable projection from your own head. This part 

 of a prawn's organization is called the rostrum. Its 



shape, its dimensions, the number and order of its teeth 

 above and below, are seized upon by the naturalist for 

 convenient specific characters. When they vary within 

 the species, as they not unfrequently do, they become as 

 specific characters very inconvenient. But all the prawn 

 wants with them is that they should be characters incon- 

 venient to his enemies. To fishes, such as are 

 found sometimes with a small museum of fish- 

 hooks inside them, the sword of a prawn may 

 make no difference. Such a fish will swallow the 

 prawn, sword or no sword. But the fact that we 

 cannot defend ourselves against earthquakes and 

 thunderbolts is not a reason for exposing our- 

 selves defenceless to a multitude of smaller 

 mischiefs. Probably the serrate rostrum of the 

 prawn is not intended for attack, so much as to 

 ward off objectionable advances, and, in the last 

 resort, to induce a disgust for an other-wise much 

 appreciated flavour by lacerating the gullet and 

 stomach of small-sized aquatic epicures. The 

 latter way of teaching them not to do it again 

 must be expensive to both parties, and one may 

 speculate whether it becomes efficacious by the 

 extinction of the gourmands, or by some subtle 

 spreading of experience throughout their tribe. 

 In some prawns the rostrum is supplemented by another 

 and a more dangerous - looking weapon. The plate 

 attached to the second joint of the second antennsF, 

 which is often broad, and has the function of a float 

 or balancer, is in Oplophorus, the Weapon-carrier, trans- 

 formed into a sharp pike. Unlike the rostrum, which is 

 almost always immovable, this bayonet-like organ can be 

 turned about to give the enemy an oblique or sideways 

 thrust, an uncomfortable dig in the ribs, well qualified to 

 teach a small fish to control in future an unchastened 

 appetite. 



In the last chapter, the Squillidse were referred to as 

 a sort of pirates, lurking in their submarine tunnels — on 

 the pounce. In this small, peculiar group, Nature shows 

 no squeamishness. It is not for meek humility of self- 

 defence, but evidently for rapine, that they are endowed 

 with their raptorial claws. In the reckoning of ap- 

 pendages these correspond with the second maxillipeds, 

 which are rather feeble mouth-organs in the crab, the 

 lobster, and the shrimp. Far otherwise is it with their 

 character in the SquiUida, and in the great Squilla 

 raphidea of the Pacific Ocean they attain a remarkable 

 development. The two last joints, often spoken of as the 

 hand and finger, may well arrest attention. The finger 

 has its inner margin divided into eight sharp graduated 

 sabre-like teeth, and in repose it shuts like the blade of a 

 clasp-knife into a groove along the hand or handle. This 

 groove itself is margined with several unequal spines at 

 right angles to its outer edge, and three long ones making 

 acute angles with its inner border. When the Sijuilla is 

 pleased to close this piece of machinery with a sudden snap 

 upon a passing object, only a very tough customer can 

 hope to escape from that death-dealing labyrinth of teeth 

 and spines. 



However fierce and formidable a few of the Crustacea 

 may look, we need not attribute to any of them ambition, 

 the desire of conquest, or the love of domineering for its 

 own sake. All those virtues they leave to us, but for 

 themselves they want food and offspring and personal 

 safety. Unless these can be secured, it is of no use to say 

 to them, " Down with your arms." They won't listen. 

 Their otoliths, or earstones, will not vibrate in response to 

 your appeal. But many of them are willing to obtain their 

 ends by very quiet methods. Without venturing to affirm 



