10 LIVERPOOL BIOLOGICAL SOCIETY. 
noticed in any abundance in the neighbourhood. Has, 
then, the Hydrobia in this locality acquired the habit of 
laying its eggs upon its neighbours’ shells as being the 
only comparatively stable objects to be found in the fine 
shifting sands around it? A short note on. the subject 
published in “ Nature” caught the attention of Professor 
G. Lindstrom, of Stockholm, who has written to me, 
saying:— . . . “I think there cannot be the least 
doubt that they [the egg-masses] really belong to that 
mollusc [Hydrobia ulve]}. Many years ago I isolated a 
number of them to see how they spawned and succeeded 
in finding oothece such as you describe fixed on stones, 
on seaweeds, on dead shells, etc., not only on the shells 
of Hydrobia.”’ He refers me to a paper* in which he had 
ficured an egg-mass surrounded by sand-grains very 
similar to those we found here. Consequently the ex- 
planation which I have suggested above may probably 
be regarded as correct. It is an interesting instance of 
local conditions giving rise to a peculiar habit. 
Another case of curious distribution of young molluscs 
is to be seen in the myriads of young mussels (Mytilus 
edulis), about 1 mm. or less in length, which are some- 
times found on Caldy Blacks and some parts of Hilbre 
Island in such abundance that all projecting objects such 
as shells, zoophytes, seaweeds, &c., are almost blackened 
by the adhering masses of molluscs. Very few of these 
reach maturity—in fact most of them disappear very soon, 
being probably eaten by larger animals. ‘The interesting 
point is that the minute free-swimming larve, derived 
probably from the mussel beds on the Leasowe shore, are 
ready to settle down in large numbers upon any object 
projecting from or more stable than the surrounding 
* “ Om Gotlands nutida Mollusker,” Wisby, 1868. 
