REPORT OF THE SOCIETY 17 



Homing Instinct. 



The so-called Homing Instinct is well developed in many insects, 

 especially ants, bees and wasps. Experiments have been carried out bv 

 Fabre, Turner, Yung, Bonvier, the Peckhams, Bonnier and others, but the 

 general opinion is that the ability of many insects to find their way home 

 from a distance is not a special instinct but is due to many factors. "As- 

 sociative memory," the "retention of effects produced by previous res- 

 ponses to visual stimuli" is an important factor according to Turner who 

 believes that "ants learn to find their way. They make many mistakes at 

 first, but gradually improve. They associate different impressions — smell, 

 touch, sight, and remember certain finger-posts." 



Fabre believed that bees and wasps had "une sorte d'intuition des 

 lieux," and Bonnier takes the same view, for when bees were liberated 

 from a box carried 2 kilometres distant from the hive they made a "bee- 

 line" for the hive, although the box was separated by an intervening wood 

 from the hive. "When their eyes were obscured by blackened collodion 

 they still found their way. The removal of the antennae did not prevent 

 their return." 



Theory of Tropisms. 



The tendency of recent research on instinctive behaviour is to refer 

 it to tropism reaction, which is the result of the irritability of protoplasm. 

 This, again, is based on changes in metabolic processes. This physico- 

 chemical theory furnishes a plausible explanation why the response to a 

 stimulus is not always the same, since the response depends largely on the 

 physiological conditions of the organism at the time of stimulation. 



According to the tropism theory instincts are hereditary in the sense 

 that they reappear in succeeding generations, or whenever the conditions 

 and factors are present which bring about metabolic changes corresponding 

 to certain tropisms or groups of tropisms. The theory of tropisms explains 

 the behaviour of most insects — their movements in search of food, their 

 sexual actions, their actions in connection with the deposition of eggs on 

 appropriate food-plants, their gathering together in certain places, etc. 

 While tropisms may be linked together and specialized by natural selection 

 into complex instincts, "they are not primarily dependent on specialized 

 sense organs and nervous systems, but are fundamental properties of 

 protoplasm common to all plants and animals." {Goodrich). 



"Instincts are formed of a series of responses which must succeed each 

 other when a particular stimulus is applied and reach a pre-determined 



