THE SCHOOL OF THE SHORE 57 



keep till we come to the fresh-water haunt. 

 Less familiar is the case of a tropical shore-fish 

 (the Gaff Topsail), which has only a few eggs, 

 and lives in places where the struggle for exist- 

 ence is very keen. What is it to do? The 

 male fish takes the eggs in 

 his mouth and keeps them 

 there until they are hatched. 

 One would think it must be 

 difficult not to swallow them, 

 but he fasts all the time. 



There are many other 

 examples of "love" on the 

 seashore. The marine leech 

 or Skate-sucker (Pontobdella 

 muricata), a warty green 

 animal, is both male and 

 female at once, like earth- 



i .t f^ . FIG. 3. THE SKATE- 



worms and snails. It is a SUC ER (PONTOB . 



very careful parent, deposit- 



, . . . , A Marine Leech that 



ing the eggs in cocoons inside takes great care of itg 



empty shells of bivalves, and 

 mounting guard over them for many weeks. 

 It is interesting to find examples of marked 

 parental care on the lower rungs of the ladder 

 of life. One of the humblest illustrations is to 

 be found in a British star-fish, Asterias mulleri^ 



