BULLETIN OF THE UNITED STATES FISH COMMISSION. .'J31 



114.— FISH AND MIDINJ!." 



By A. ois TERBOL. 



It is well known that certain fish and medusae may be said to live to- 

 gether as good comrades, as several fish accompany the medusae where- 

 ever they go, and seek shelter under their swimming-bell. Thus young 

 cod frequently are found under large medusians, supposedly to seek 

 protection from their enemies, which probably are scared by the swaying 

 tentacles of the jelly-fish. The young of the mackerel likewise often 

 seek shelter under large medusae, and probably for the same reason. It 

 is probable, however, that the young fish hide under the swimming-bell 

 of the medusians, not only to escape the persecutions of their enemies, 

 but also because this place of refuge affords them easier access to food. 

 The young of fish live on microscopic animals, and this food they find 

 in the eggs and larvae of the medusaB when these have left the mother 

 animal. A kind of herring, found on the coast of America, eats not 

 only the eggs of the medusa, but nibbles at the medusa itself. It is 

 said that mackerel, when fully grown, will follow the medusae and eat 

 diminutive crustaceans found on them. A species of mackerel which 

 lives on the coast of Australia has a very sly way of seeking shelter 

 and providing its food, as, under the swimming-bell of the medusaB, ac- 

 cording to an observer, they are safe from their enemies, and without 

 the least trouble are liberally furnished with the small animals which 

 constitute their food, as the constant current produced by the medusae 

 carries many of these animals underneath their swimming-bells. It has 

 also been observed that a medusa will occasionally snatch a fish, which 

 therefore has to pay with its life for the protection which it and its com- 

 rades have enjoyed ; and small sea-nettles have also been observed to 

 eat fish -eggs. 



In this connection it may be interesting to note the observations re- 

 cently made by Dr. Hugo Eisig in the aquariums of the zoological sta- 

 tion at Naples, as they throw considerable light on the remarkable 

 relations existing between fish and medusae. 



He states that fish are frequently found under the swimming-bells 

 of the largest two medusae in the Bay of Naples, and that they are so 

 inseparably connected with them that they are frequently caught with 

 the medusae. Even in the aquarium they continually swim round tin' 

 medusians, and occasionally hide under their bells. For a long time 

 Dr. Eisig was of the opinion that the fish accompany the medusae only 

 to seek shelter from danger under the wwimrning-bells, but further obser 

 vations showed that they preyed on the medusae. Among the compan- 

 ions of these medusae Dr. Eisig observed three mackerel. A young 



* "Fiske og Meduser." From Fi8leritid&ide, No. 22, Copenhagen, June 2, 1835. Trans- 

 lated from the Danish by Herman Jacobson. 



