56 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



Pelagic Turbellaria are rare, but occasionally occur in 

 tow-nettings. Such are certain Khabdocoeles and larval 

 Polyclads. 



TURBELLARIA. 



I.— TKICLADIDA. 



1. Planaria alpi7ia, Dana (PL XII, figs. 1 and 2.) 

 This fresh-water species is about J" in length, body 

 grey, produced anteriorly into a pair of tentacles, a single 

 pair of eyes are present. I have found it in cold springs 

 near Silverdale (Lancashire) and in the sheltered gorges 

 near Port Erin. This last fact taken in connection with 

 Wm. Thompson's discovery of alpina on the East coast 

 of Ireland (which however needs confirmation) have an 

 important bearing on the geographical distribution of this 

 Turbellarian. Planaria alpina is a distinctly alpine 

 creature and where occurring at lower levels, does so in 

 water of a constantly low temperature. Dana first found 

 it in the Graubuntner Alps. It has since been found near 

 Chur and in the Davos mountains at heights of 6 — 7000 

 feet and in water at a temperature of 2°C which is frozen 

 from November to May. v. Kennel (in a most interesting 

 paper, (Zoologische Jahrbiicher, III, p. 447), to which I 

 am greatly indebted) has found it in the Maine Valley at 

 Wiirzburg at the outflow of a spring (temperature 10°C). 

 The effect of a higher temperature than this is readily 

 seen when attempts are made to keep these animals 

 indoors. As soon as the water rises above IS'^C they die 

 very rapidly. 



With these facts in mind v. Kennel has attempted their 

 explanation. The difficulty is this, how did Planaria 

 alpina get from Switzerland to Wiirzburg, England, 

 the Isle of Man and Ireland ? The tendency to explain 

 this and similar cases by saying that alpina is a " Belickt- 



