The Worms and some of their Posterity 



transport of nutritive substances to the various parts of the body. 

 In the Nemertines the second of these functions is carried out 

 by the blood system, which consists of two or three vessels that 

 run parallel throughout the length of the body and anastomose 

 at either end. There is no indication of any enlarged or specially 

 contractile portion of any of these, no indication, that is to say, 

 of a heart. The blood conveys not only nutritive substances, 



FIG. 43. Nephridium of a Turbellarian. 



but also, as in the higher animals, oxygen. Some Nemertines 

 have indeed red blood, containing true haemoglobin, which is 

 well known as the oxygen-carrying material in the vertebrates. 

 A typical Nemertine is shown in Fig. 44, and a diagram showing 

 some features of the anatomy in Fig. 45. It will be seen that the 

 nervous system is of the same type as in the worms already de- 

 scribed. There are two pairs of sense organs, one pair being eyes, 

 and the other probably having the function of gauging the chemi- 



63 



