284 Silk Manufacture. 



careous valves afford a shelter to her guest, while he makes a re- 

 turn for this protection by going forth in search of prey. At these 

 times the pinna opens her valves to afford him egress and ingress : 

 if the watchful scuttle fish now approach, the crab returns imme- 

 diately with notice of the danger to her hostess, who, timely 

 warned, shuts her door and keeps out the enemy. When the 

 crab has, unmolested, succeeded in loading itself with provisions, 

 it gives notice by a gentle noise at the opening of the shell, and 

 when admitted, the two friends feast together on the fruit of its 

 industry. It would appear an arduous, nay, almost an impossible 

 task, for the defenceless and diminutive crab, not merely to elude 

 its enemies and return home, but likewise to obtain a supply of 

 provender sufficient to satisfy the wants of its larger companion. 

 The following different account of the nature of this alliance is 

 much more in agreement with probability : — 



' Whenever the pinna ventures to open its shell, it is immediate- 

 ly exposed to the attacks of various of the smaller kinds of fish, 

 which, finding no resistance to their first assaults, acquire bold- 

 ness and venture in. The vigilant guard, by a gentle bite, gives 

 notice of this to his companion, who, upon this hint, closes her 

 shell, and having thus shut them in makes a prey of those who 

 had come to prey upon her : when thus supplied with food she 

 never fails to share her booty with so useful an ally, 



' We are told that the sagacious observer. Dr. Hasselquist, in 

 his voyage about the middle of the last century to Palestine, 

 which he undertook for objects connected with the study of nat- 

 ural history, beheld this curious phenomenon, which, though well 

 known to the ancients, had escaped the attention of the moderns. 



' It is related by Aristotle that the pinna keeps a guard to watch 

 for her, which grows to her mouth, and serves as her caterer : 

 • this he calls pinnophylax, and describes as a little fish with claws 

 like a crab. Pliny observes, that the smallest species of crab is 

 called the pinnotores, and being from its diminutive size liable to 

 injury, has the prudence to conceal itself in the shells of oysters. 

 In another place he describes the pinna as of the genus of shell- 

 fish, with the further particulars that it is found in muddy waters, 

 always erect, and never without a companion, called by some 

 pinnotores, by others pinnophylax ; this being sometimes a small 

 squill, sometimes a crab, which remains with the pinna for the 

 sake of food. 



' The description of the pinna by the Greek J)oet Oppianus, 

 who flourished in the second century, has been thus given in Eng- 

 lish verse : — 



