Curious Creatures 209 



which live in salt water. Here is to be louiul every 

 type, from the low^est to the highest, from the most 

 abhorrent to the most attractive, and forms which in 

 richness, variety, or harmony of color are not surpassed 

 even by the exquisite tints of the comb jellies. All 

 show marvelous adaptation to their environment, many 

 exhibit uncommon ingenuity in the construction of their 

 homes, and not a few betray an intelligence that is 

 superior to numberless creatures more highly organized 

 than they. In truth, the simple organization of the 

 worms when contrasted with the complex life histories 

 often prevailing among them, is one of the greatest 

 marvels in natural science. So involved is the develop- 

 ment of some of the most abundant forms that years 

 of patient investigation have not yet determined its 

 exact nature. 



Perhaps the strangest puzzles occur among the flat 

 worms, the lowest of all worms. There are some 

 which begin life as males, but later in life they lose 

 their masculine characteristics and become females. 

 Others, again, seem to have lost all functions of sex, 

 reproducing their kind by dividing into several pieces, 

 each piece, after growing into a perfect adult, repeating 

 the process. 



The largest of the flat worms, and, for that matter, 

 of all worms, are contained in the nemerteans, a class 

 characterized principally by the long, narrow, pro- 

 trusible proboscis carried by the individuals. A com- 

 mon type is the ribbon worm {Meckelia ingens). This 

 animal is found in tide pools secreted under stones or 

 buried in the sand between the tide marks. Its length 

 when full grown is ten feet or more; its breadth Is 



