Amiphipoda balcanica. 103 



ď A r s a-A r s a in the whole run, the rivers T i m a v o and 

 Tagliamento). The forms in the sea and near the mouths 

 of the rivers háve a very well developed carina. The forms 

 which advanced in the rivers háve a very reduced carina. 



The samé phenomenon we can observe with Gammarus 

 pungens. Specimens f rom the f reshwater near of the sea háve no 

 carina, but they are pressed a little from the sides so that 

 we can distinguish two forms: Gammarus pungens f. carinata 

 and Gammarus pungens f. acarinata. (far of the sea). 



G. pungens in the N a r e n t a district are living in the 

 springs during the constant, not low and not high, tempe- 

 ra ture. The re are two possibilities of the G. pungens living 

 in these localities. It is possible that the ancestors of the 

 G. pungens are immigrants from the sea into the water many 

 thousand years ago, perhaps at the time of the so called 

 sea transgression in the continent. G. pungens as a form from 

 the sea, where there is not so large temperature-oscillatiori, 

 i. e. as a stenotherm form chooses the springs, where tlie 

 temperature is also constant. 



4. The distribution of Gammarus halcanicus m i h i 

 and his relation to the forms Gammarus spinicau- 

 datus mihi and ko7ijicensis mihi. 

 G. halcanicus is a wide-spread form in the Balkán 

 regions (Montenegro, Hercegovina, Bulgaria) and 

 also in the heighest mountains (Vitoša 1000 m) with the Pia- 

 naria montenegrina and Pl. alpina, G. halcanicus are related 

 to the G, spinicaudatus and konjicensis, but being influenced 

 by the environment the spinules on the urosom are reduced. 



5. Distribution of Gammarus komáreJci mihi. 



This form aecording to discoveries we know lives in 

 warm waters in the district south of the Balkán mountains, 

 and east of the Rhodope mountains, where these species are 

 living with the Telphusa fluviatilis and Emys orhicularis. G. 

 JcomáreM belongs to the relation of G. syriacus and is so 

 an exponent of an old f amily of Asia Minor, but it has been 

 geographically separated from the originál family after the 

 formation of the Dardanelles. 



