39- Papers from the Marine Biological Laboratory at Tortugas. 



the second and third were refused. Three formahn reds were then thrown 

 and all refused. The 3 sorts of atherinas, 3 of each, were again offered 

 immediately and in the same order. The formalin normals were taken, the 

 reds, both tcntaclcd and untontacled, were refused. 



Since the tentacles project slightly from their months, formalin tentaclcd 

 red atherinas differ from normal fish not only in color, but also in form. 

 The snappers might therefore recognize them as unpalatable cither by reason 

 of their color or form or by both characteristics. That the snappers actually 

 form an association between the disagreeable quality of tlie red tentacled 

 atherinas and their color is shown by their refusal to take red atherinas 

 which are not tentacled. As a further test. 20 formalin tentacled atherinas 

 (uncolored) were offered to the laboratory colony of snappers at 1^ 15" 

 p. m. on July 19, 1907. Five formalin normals were first thrown and these 

 were followed by the 20 formalin tentacled normals. All were taken with- 

 out hesitation. Several red fish, some tentacled, others untentacled. were 

 then thrown and remained for some time untakcn, but were finally taken. 

 The fact that white fish with tentacles are taken at once is evidence that the 

 discrimination is by color, not by form. That red fish are still taken, though 

 after much hesitation, is probabl\ due in part to their having been offered 

 immediately after a considerable number of formalin normals, in part to the 

 presence in the colony of snappers whose individual experience of the un- 

 palatable red was not yet suflicient to give to the color a warning signifi- 

 cance. Such irregularities are to be expected in dealing in mass experi- 

 ments with an entire colony of snappers. That experiment 32 gave to the 

 color red a warning significance for the snappers, so that red atherinas 

 were afterward for some time protected from their attacks by reason of 

 their color, is shown in the next section of this paper. 



The details of the behavior of the snappers toward the various sorts of 

 atherinas used is of interest as enforcing the conclusion drawn from the 

 tables and is here abstracted from my notes. 



(a) Formalin normals at the beginning of the series. — The atherinas are 

 taken when they strike the water. All the snappers rush at them and the 

 successful fish snap so vigorously that they send spurts of water above the 

 surface as they strike it with their tails in turning. 



{b) Formalin tentacled reds. — These were taken quickly at first, but in a 

 different manner from the formalin normals. The snappers did not rush 

 at them with so much vigor as to produce a splash at the surface. As the 

 feeding continued the tentacled reds were taken with increasing hesitation. 

 Most of those taken were then approached deliberately. If the approach 

 brought the snapper into contact with the tentacles he at once jerked back. 

 This he sometimes appeared to do without contact with the tentacles. Some- 

 times the snapper jerked back upon contact with the sides of the atherina. 

 This approach and retreat was often several times repeated by the same 

 snapper. If an atherina was taken after being thus approached it was taken 

 gingerly by the side or tail in such a way that the snapper did not come into 



