T. Kirk. — Displacement of Species in Nciu Zealand. 3 



and even mammals, whether introduced purposely or acci- 

 dentally, affect alike both fauna and flora. 



Naturalisation, Displacement, etc. 



It may be advisable to remind you that a plant or animal 

 is said tobe naturahsed in a new country when it has become 

 so thoroughly established as to be able to perpetuate itself 

 spontaneously. The term, however, must not be confused 

 with acclimatised, which, as popularly used, conveys the 

 erroneous idea that the organization to which it is applied 

 has been specially adapted to its new environment by having 

 passed through a series of changes. What is called " ac- 

 climatisation " is based on the snnple fact that many plants 

 and animals are able to flourish under conditions differing 

 from those under which tliey were originally placed. 



Displacement, although usually attended by a diminution 

 in the number of individuals, is sometimes accompanied by 

 increase, as is the case with those insects which now obtain a 

 large supply of food from introduced plants, and consequently 

 exhibit a vast increase in numbers. Eeplacement can only be 

 said to occur when the naturalised organism occupies the 

 position of that which it has displaced ; the displacement 

 being approximately, although perhaps not actually, com- 

 plete. On the other hand, complete displacement is not 

 always followed by immediate replacement. The tuatara 

 (Sphenodon punctatum), for instance, has been all but de- 

 stroyed on the mainland by the wild pig and the cat, but 

 these cannot be said to have taken the place of the tuatara 

 — their agency has been wholly destructive. On the other 

 hand, the place formerly occupied by the Maori rat in the 

 North Island is now so fully occupied by its old enemy the 

 black rat as to afford a striking instance of complete replace- 

 ment. It will be useful to bear these distinctions in mind 

 when considering the influence exerted by introduced organ- 

 isms on the flora and fauna of any country. 



It is not proposed to consider in detail the effects produced 

 by naturalised organisms on the flora and fauna of the colony, 

 but merely to draw attention to various cases, more or less of 

 a typical character, and to state the general results so far as 

 they have been ascertained. 



Invertebeata. 

 Although there is some probability that certain species of 

 Infusoria, Eotifera, and possibly Hydrozoa have been intro- 

 duced into the colony, there is no direct evidence to that 

 effect ; while so little is known respecting either native or 

 introduced Entozoa, beyond the fact that several species have 

 made their appearaiace here as uninvited guests, that atten- 



