iS6 NATURE'S CALENDAR 



August 22 



cess; and their stout masses are often of 

 great service in resisting the wearing away 

 of the soil by the currents. All these bi- 

 valves, like the oysters, increase by pour- 

 ing forth, in midsummer, an immense 

 number of eggs that drift about in the 

 water, the prey of multitudes of aquatic 

 creatures, so that only one in a thousand, 

 perhaps, ever is hatched, and few of these 

 survive long enough to come to maturity. 

 The univalve mollusks— those whose 

 shells are all in one piece and usually 

 spiral— such as the sea snails, periwinkles, 

 etc., on the contrary, lay few eggs, but 

 place them where they are subject to far 

 less dangers. You will be sure to find, 

 this month, along the sands curious skeins 

 of yellowish lozenge-like cases, looking 

 something like a toy snake. These are the 

 egg cases of the large pear-shaped wnnkles, 

 or conchs, whose dead-white shells, be- 

 reft of their brown, hairy skin are thrown 

 up from the deeper water in every storm, 

 and may always be obtained alive on the 

 oyster-beds, where they do vast damage. 

 They can move about rapidly, walking 

 upon a broad muscular surface pushed out 

 from the shell, which is dragged along like 

 a burden ; and they feel their way by the 

 help of two tentacles projecting forward. 

 Just beneath them is a mouth which may 

 be protruded and enlarged so as to envel- 

 op and crush an oyster or similar victim, 

 whose juices are then sucked out. In the 

 absence of such living prey these and 



August 23 



