uS 



SYSTEMATIC ZOOLOGY 



distinguishes the Nemertina from the Platyhelminthes. In many 

 of the Nemertina the nervous system is more highly developed 

 than in the flatworms proper. It consists of a brain, made up of 

 two ganglionic masses, connected with two nerve cords extending 



longitudinally through the 

 body and connected with 

 one another by numerous 

 transverse branches. Eyes 

 are present in varying 

 numbers. There is no 

 distinct body-cavity. The 

 excretory system consists 

 of branched tubules, and 

 the reproductive system 

 of simple ovaries, the 

 female germ-glands, and 

 testes, the male germ- 

 glands. The sexes are 

 generally separate, and 

 the development is usu- 

 ally by means of larvae ; 

 a very characteristic larva 

 is the pilidium (Fig. i 10), 

 which resembles a Greek 

 cap. 



Many of the Nemertina 



J 



are very small, only two 



millimeters in length, while 

 some have been found 

 "*^~^^~^ over thirteen meters long 



FIG. 108. Cerebratulus montgomeryl, one of the an( J J egs tnan Qne cent i- 

 Nemertina found on the Pacific coast ; it is bright 



red in color and often ait.uns a length of two meter broad ; but all are 



meters. (From a drawing furnished by Dr. W. R. verv contractile and CX- 

 Coe.) 



tensible. The colors vary 

 greatly and are often verv beautiful, while some species are very 

 curiously marked with longitudinal and transverse lines of con- 

 trasting colors (Fig. in). Even when carefully handled the 

 body breaks up into several pieces, so that it is often difficult 

 to secure an entire animal ; under favorable circumstances the 

 pieces may develop into complete worms. 



