INTELLIGENCE IN LOWER VERTEBRATES 225 



the aquarium. In its endeavors to reach its nest the goby 

 swam against the glass partition ten tunes and then found 

 the passage. It was then driven from its shell into the 

 adjoining compartment again. It now rammed its head 

 against the partition six times, then found the passage and 

 entered its shell. In the next trial the fish made only three 

 or four attempts to go through the glass plate, and after 

 this it found the passage way at once. In a short time the 

 fish had learned the way to its nest and thereafter followed 

 it with little hesitation. 



After this set of trials the goby, now left to itself, began 

 to explore the aquarium of its own initiative, by making 

 excursions farther and farther from the nest, keeping close 

 to the outer wall and returning each time by the same route 

 by which it set out. When it arrived at the partition it 

 bumped against it, but after two or three trials it stopped 

 a little short of the barrier and continued to do so in its 

 subsequent excursions. 



After the habit of avoiding the glass plate had become 

 well established the plate was removed. The goby never- 

 theless continued to follow the old path hi its journeys to 

 and from the nest. Even when the fish had happened two 

 or three times to cross the place where the partition had 

 been, it still persisted in taking the old round-about course 

 from one part of the aquarium to the other. Finally after 

 the fish had crossed directly several times the old habit 

 became gradually broken up and the fish paid no attention 

 to the place where the partition had been located. In one 

 interesting experiment Mile. Goldsmith filled the shell of a 

 goby with mastic and placed it in its old position. The 

 goby came to its shell and endeavored to get under it, trying 

 first its accustomed point of entrance, and then making 

 attempts to dig under it in various other places. It dug 



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