358 TRANSACTIONS LIVEErOOI. BIOLOGICAL SOCIETY. 



tliey very soon found and attached themselves to the fish 

 that had been caugdif. Tlie wlielk proceeds by borin^ a 

 liole throug-h tlie skin, inserting^ its snout, and then 

 devoiirinof all the muscular tissue, leaving nothino- but 

 skin and bones. The mollusc will not touch rotten fish, 

 but experiments have shown that it will devour anything 

 so long as it is fresh. Often enough, 10 to 20 whelks 

 would be found attached to a plaice, and the fishermen 

 estimated that one-third of the year's catch was lost in 

 the region investigated (Thisted Bredning, in Denmark). 



The experiments carried out by Petersen were of a 

 two-fold nature — (1) to determine the number of whelks 

 in a certain area, and (2) to find out whether these could 

 be economically exterminated by capture. The first 

 part of the work was carried out by using an instrument 

 called the " bottom-sampler," and also by the employ- 

 ment of a diver. The latter caught from 106 square 

 metres 100 whelks, 36 square metres 128 whelks, lOG 

 square metres TO wlielks, 106 square metres 97 whelks. 

 In the last two cases the man reckoned that he had 

 only taken one-third of the whelks present. From the 

 results it was calculated tliat 1-30 million whelks were 

 present in the region (an area of 65 million square 

 metres). 



One motor boat, witii 240 traps, was able to catch 

 3,845^ bushels (45 tons of whelks I) in the same district, 

 between April 5th and Novembci Slli. 



On the whol(», it was concluded that the extermina- 

 tion l>y catching would not b(> an economic metliod, 

 especially since there did jiot seem to be anv gr(>at use 

 for the whelks caught in the district. Petersen also 

 states tliat six or seven wlielks" ojjcrcula may be found in 

 one cod's stomacli. ami commeuts on tht- raril\- oi' anv 

 remains of t lie sliclls. 



