ON THE BREEDING HABITS OF ECHINUS MILIAEIS 257 



ready to spawn they gather more or less closely together," and Hertwig* 

 mentions that " egg-deposition may provide sexual stimulation to the 

 males, since when a large number of urchins are placed together in sea- 

 water as soon as the females begin to discharge eggs the males spawn." 

 It is not improbable, therefore, that association of the sexes for the 

 purpose of spawning may be common throughout the Echinoids. 



Note on the Feeding Habits of Patella. 



It is well known that Patella obtains its food by browsing on both 

 the smaller and larger forms of algae. f Striking evidence of this fact has, 

 however, been obtained and is worth noting. In observing specimens of 

 Patella situated on cement piles above low-water mark, it was noticed 

 that the animals had in many cases eaten away paths in the green algae, 

 chiefly young Enteromorpha, by which they were surrounded. The paths 

 radiate from the " scar " of the animal, and are marked with fine lines 

 made by the teeth on the radula. These paths are shown in Fig. 1. 

 In several cases the animal had travelled beyond the end of the path 

 formerly eaten before beginning to browse again, and afterwards re- 

 turned home to its scar. (See Fig. 1.) Such configurations as that 

 shown in the figure are by no means uncommon on the pier walls in this 

 district in situations favourable for the growth of algae. As the alga 

 grows the food-paths of the limpet may become more marked, and in 

 some cases the spatting of Balanus balanoides along the paths makes 

 them so evident that they are easily seen from some distance away. 



* 0. Hertwig, Zeit.filr Wiss. Zool. Jen., Vol. XXIV, p. 282, 1890. 

 t J. R. Aiiisworth Davis and H. J. Fleiire, Patella L.M.B.C. Memoir, Yol. X,, 

 London, 1903, 



