AQUATIC ORGANISMS AND EXTERNAL METABOLITES 511 



the internal metabolites of their hosts. Can we now be quite sure 

 that some at least of the marine metazoa, particularly in their 

 youngest stages, are incapable of maintaining themselves in similar 

 ways, wholly or in part.-* 



10. May I now mention one or two examples of aspects of the 

 behavior of marine organisms which are now only just beginning 

 to be understood? First, following the early observations of Nelson 

 on the pumping reactions of the oyster, Allison and Cole (1935) 

 demonstrated a relationship between the feeding reactions of the 

 barnacle and the local phytoplankton abundance, while Collier 

 et al. (1953) further demonstrated a specific pumping reaction in 

 the oyster to the variable free carbohydrate content of the water. 



Again, Davenport and Norris (1958) have just shown how the 

 small fish Amphipyron, apparently via a mucus secretion, influences 

 the anemone Sioichthys so that gradually a state of tolerance is set 

 whereby the fish can come to live among the tentacles of the 

 anemone without harm and possibly with benefit. A fundamental 

 behavior reaction toward fish and other animals in general is thus 

 regularly changed via an ectocrine process when members of 

 these two species come together. Other examples of this type of 

 ecological modification of behavior are sure to be found. 



My next example concerns the apparent homing responses of 

 some fishes to free organic substances derived and carried by 

 currents from their "homes," to which they presumably became 

 conditioned during early life (Hasler, 1954). Here we may also 

 have a clue to the problem of the more generalized "homing" of 

 so many sea fish, whereby the annual drift of their planktonic eggs 

 and larvae away from the spawning centers has to be counter- 

 balanced by the annual return of the adults to spawn in approxi- 

 mately the same places. This is not to suggest that these important 

 movements are governed only in such ways. Yet, whatever parts 

 they may play, response to postulated orientations by natural 

 light or geographical "memories" still seem inadequate to account 

 for some of the homing reactions which observations seem to 

 demand. 



This last may seem to be the most speculative of all and yet, as 

 modern human beings, we are perhaps particularly ill equipped to 



