2o6 The Irish Natiaalist. September, 



Locomotion and the Use of Slime threads in Irish Marine 



Mollusca. 



In a valuable paper {Ann. Mag, Nat. Hist. (S), vol. iii., April, 1909, 

 pp. 354-362), N. Colgan gives the results of his observations on the loco- 

 motive powers of some species of marine Mollusca, chiefly Gastropods, 

 and more especially on the use made of the slime-threads as an aid to 

 locomotion. Mr. Colgan begins by remarking that "every student of 

 the marine Mollusca is familiar with the fact that the Gastropods in 

 general have a strong propensity to float foot upwards on any still-water 

 surface the}' may be enabled to reach b}^ crawling, and thatman}- of them 

 are accustomed to suspend themselves beneath that surface by means of 

 slime-threads or attenuated strings of the mucus which all of them so 

 freely secrete." 



After referring to Gray's and Wallis Kew's statements on the power 

 possessed by a few of our native species of marine Mollusca of re-ascend- 

 ing to the surface of the water by means of these slime-threads, Mr. 

 Colgan states that out of eighteen County Dublin species placed under 

 observation last year no less than ten were seen to climb up along their 

 suspensory slime-threads to the surface of the water from which they 

 had descended ; he has moreover little doubt but that further observa- 

 tions would have shown many others of the eighteen to possess the same 

 power. He then proceeds to give details of the behaviour of the ten 

 species observed to climb by their suspensory threads. 



Mr. Colgan also noted the rates of vertical travel up the sides of 

 graduated glass tubes of 16 out of the 18 species placed under observa- 

 tion ; the slowest rate of travel was observed in two species of Rissoa, 

 which took 3 minutes to travel i inch, and the quickest rate in two 

 species of Eolis (^E. Farrani and E. Drjtmmondt) which took only 15 and 

 13 seconds respectively to do the same distance. 



The Char of Lough Currane. 



I am indebted to Mr. W. M'EHigott, of Waterville, for a Char caught 

 by him in Lough Currane. The specimen is of interest, as it l)elongs to 

 the form named Salvelinus Colii, previously known to occur only in 

 Galway and Southern Donegal, and differs considerably from the Cooma 

 saharn fish (5. finilm'ahis), or the Char of Acoose and Killarney (.V. obhisiis) 

 The Currane fish presents all the characters mentioned by me as distinc 

 tive of .S". Colli {/ris/i Natin-a/isl, 1909, page 4). and appears to l)e absolutely 

 identical with examples from the type locality, Lough Raske, in Donegal 

 The wide range of 5. Colii is in harmony with my supposition that it is 

 the most generalized type of Irish Char. 



I shall be very glad to have Char from any part of Ireland, and I hope 

 that readers of the Irish Naturalist may be able to send me some. 



C. TaTK RkCxAN. 

 British Museum (Natural History), 

 London, S.W. 



