THE SEA SHORE 51 



with up to ten whorls, the edges of the ribbon being 

 scalloped or the whole zig-zagged in its course, and usually 

 white or 3'ellow in colour (Plate 17), though that of the 

 common >^olis is pink and ropy. 



The eggs of the crustaceans are usually carried by the 

 female— either in special chambers on the under side of the 

 body called " brood pouches " or, in the more highly- 

 organized crabs, prawns or lobsters, attached to the swim- 

 ming legs — until the early stages of development have been 

 passed, which may take several months, so that the young 

 leave the parent, not as defenceless eggs or embryos, but as 

 actively swimming " larvae," a full account of which is 

 given in Chapter V. A crab or lobster which is " in berry " 

 is probably familiar to everyone, and shows this condition 

 clearly. In the sea spiders the male carries the eggs, 

 which are handed over to him in a bundle by the female as 

 soon as they are laid. 



The effect of different conditions on the spawning of 

 shore animals is very strikingly shown by the spawning 

 habits of the different kinds of periwinkles. The kind which 

 lives nearest low-water mark lays its eggs in little capsules 

 from which the young hatch out at a very early stage as 

 tiny swimming creatures ; the young of the periwinkle 

 which occurs about the middle of the shore hatch out at a 

 later stage though still requiring water to swim in, while 

 those of the periwinkles which live near, or even above, 

 high-water mark are produced as miniature editions of their 

 parents, and able to crawl about on exposed rocks at once. 

 These differences are connected with the increasing lack of 

 water, for the earlier the stage at which the periwinkles 

 are hatched, the longer they will need water in which to 

 swim before they settle down on the shore. 



Not all animals reproduce themselves sexually. Some 

 bud off pieces of themselves, divide in two or break up into 



