Crustacea. 4697 



cranny, around and partially under the pebbles and rock-work, and 

 often into the tubes of Serpulae or Sabellae, or the shells of the uni- 

 valve mollusks and others ; and these, if not protected by an opercu- 

 lum or some provision for closing the orifice of their tube or shell, 

 soon fall a prey to their attacks. When anything edible is met with, 

 it is rapidly seized by these prehensile feet and transferred to the 

 jaws. 



The senses of touch and smell in the Palaemonidae are exceedingly 

 delicate, the latter appearing to reside most strongly in the antennae. 

 Thus, when a small particle of food has been dropped into the water 

 and has sunk to the bottom, the moment the antennae of the prawn in 

 its movements pass across the column of water through which the food 

 has fallen, the whole motion of the creature becomes changed in an 

 instant, and it darts rapidly here and there, from the surface through- 

 out the path of its transit until it is discovered ; and often, after it 

 has been devoured by the one, a second prawn will, on reaching the 

 same locality, gain the scent and hunt over every spot in search of 

 that which had been already removed, but which evidently had left 

 its track of odour behind. It has very often occurred, that if some 

 one of the Actiniae had been first fed, the Palaemon, on gaining the 

 scent, has tracked the food to the Actinia and speedily rifled it of its 

 repast; and, in instances where the latter had even transferred its 

 meal by means of its tentacula to its pouch, the prawn has redoubled 

 its efforts, and frequently dragged the savoury morsel out of its very 

 stomach. This operation it effects in a very surprising manner: the 

 Palaemon charges, without any apparent fear, full on the extended 

 disk of the Actinia, the tentacula of which it keeps in constant play 

 by means of its three pairs of unarmed feet, while, at the same time, 

 one of the second or larger pair of prehensile feet is thrust into the 

 orifice of its maw, and the food forcibly and quickly extracted. The 

 only chance the poor Actinia has of preventing this and securing its 

 feast appears to be by contracting the whole of its tentacula together, 

 and thus forming itself into a small globular form, so as to close en- 

 tirely all approach to the orifice of its stomach. The energy with 

 which this attack is effected depends very much on the keenness of 

 the prawn's appetite, and, in cases where the Actinia is strong and also 

 very hungry, the conflict is often very severe, and the aggression is 

 sometimes, though rarely, successfully repelled. 



The first pair of didactylous feet are slender and most delicate in 

 their structure, and, when examined with a magnifying glass, are 

 found to be provided at their extremities with a brush-like appendage 



