THE SEA-SLUGS. 253 



alone. Possibly the slime with which they are covered has 

 something to do with their immunity. They have a curious 

 habit of congregating, not in pairs, but in clusters of three 

 to seven or so, and laying their eggs in continuous masses. 

 The eggs are embedded in a tenacious jelly analogous to that 

 which surrounds the eggs of frogs. By means of this jelly 

 not only are the eggs attached together to form a ribbon 

 about half an inch broad, but also one side of the ribbon is 

 sufficiently sticky to adhere to the rock surface, and as the 

 ribbons are laid in spirals, they stand up from the rocks like 

 ladies' frills. Such ribbons are found on the rocks during 

 almost all the colder months of the year, but are most 

 abundant in February and March. 



You should not fail to obtain a small stone bearing spawn, 

 and carry it home with you to place in an aquarium. By 

 means of a lens you can make an attempt to estimate the 

 number of eggs in an inch of the ribbon, and so get an idea 

 of the countless numbers of eggs laid by each individual. A 

 few pages back we discussed the egg-laying habits of the 

 whelk, and noticed the wholesale sacrifice of eggs which 

 takes place within the egg-capsule. Nothing of the kind 

 occurs here. If you are successful with your spawn you 

 will find that from each egg a tiny colourless larva hatches 

 out, so that the water of your aquarium becomes cloudy 

 with the myriads of swimming specks. These larvae are 

 very diS'erent from the adults, and for a time are furnished 

 with the shell which the adult has lost, and with a power of 

 swimming of which the adult shows no trace. Stir the 

 water in your aquarium gently, and notice how at every 

 movement hundreds of larva? are thrown up on the sides of 

 the glass, there to speedily perish. Think of the wash of 

 the sea over the shore rocks, of the dangers from enemies, 

 and you will realise that, ruthless as the methods of the 

 young whelks seem, they are probably justified in their 

 results. It is probably better that many of the eggs should 

 be sacrificed to feed the few, if these few are thereby 

 enabled to remain within the egg-case until the early stages 

 of their development have been passed through, rather than 

 that all the eggs should be hatched in a condition when 

 their power of resistance to unfavourable conditions is very 

 slight. On the other hand, it should be noticed that the 



