37 



probably by proximity to some iron-laden stream. These 

 cockles seemed to be otherwise normal, and perfectly 

 healthy. 



In some parts of the district there is usually a filamen- 

 tous brown tuft appended to the posterior (upper) end of 

 the animal, which the fishermen believe to be a part of the 

 body, and to be, when seen projecting from the sand, a 

 sure indication of the presence of the cockle. Mr. Dawson 

 drew my attention to the matter during a visit in May to 

 the cockle and mussel beds in Morecambe Bay, and on 

 obtaining specimens and examining them I found that the 

 tuft consisted in many cases of the zoophyte Obelia flabel- 

 lata and in other cases of a filamentous Alga (sea-weed — 

 a species of Sphacelaria). Both Zoophyte and Alga are 

 attached to the extreme posterior edge of the valves which 

 is, in the natural position of the animal, the part which is 

 highest or nearest to the surface of the sand. Of course 

 the tuft of Zoophyte and Alga have no special connection 

 with the cockle ; and their fairly constant presence in 

 some localities is merely due to the circumstance that 

 the cockle shells are, compared with the sand grains by 

 which they are surrounded, relatively stable objects to 

 which the free swimming young stages have attached 

 themselves as they would to a rock — and they have chosen 

 the posterior end of the shell because that is the point 

 nearest to the sea above, from which they came and into 

 which they must project. There is absolutely no ground 

 for the idea that the tuft is in any way injurious either to 

 the cockle or to the person who eats the cockle. 



The cockle in our neighbourhood spawns in summer. 

 The specimens dissected in the laboratory in June and 

 July were many of them mature males and females 

 with fully developed ova and spermatozoa. The number oi 

 ova laid is very great, but of course a large proportion are 



