340 OUTLINES OF EVOLUTIONARY BIOLOGY 



Dr. Macculloch, in the Transactions of the Linnean Society, as 

 far back as 1801. I am enabled by the courtesy of the Council 

 of the Society to reproduce here, on a reduced scale, Dr. Maccul- 

 loch's original plate (Fig. 172). The crab actually breaks off 

 fronds of seaweed and attaches them to the long hairs of its body, 

 thus disguising itself so effectually as to be quite unrecognizable 

 except by careful examination. Dr. Macculloch was of opinion 



FlG. 172. Reduced Facsimile of Dr. Macculloch's Plate of Macropodia 

 rostrata, in the Transactions of the Linnean Society. On the left is 

 shown a plant of the seaweed in which the crab dresses itself up ; on 

 the right the crab without the seaweed, and at the bottom the crab 

 dressed up. 



that this dressing up of the crab in seaweed was an artifice 

 which assisted it in capturing its food (anticryptic), but it is 

 much more likely that it is protective (procryptic). The late 

 Professor Bell has told us how the slow and sluggish habits of 

 the crab render it an easy prey to fishes, and the stomach of a 

 thornback ray has been found entirely filled with them, so that 

 there appears to be ample reason for them to seek concealment. 



In the case of Macropodia the adaptation for concealment 

 shows itself as an inherited habit or instinct more than in any 

 modification of bodily structure, but such an instinct is probably 



