MEANS OF TAKING IN FOOD. 



47 



secure food, to divide it, and to transmit it to the stomach after- 

 being well comminuted ; while man also requires the assistance 

 of the cook in the preparation of his food. Now although 

 from a physiological point of view, these auxiliary organs are of 

 less importance than the digesting intestinal canal, they are of 

 the highest interest for us, inasmuch as they involve an endlessly 

 varied series of links between animals and the conditions under 



Fig. 12. — Sacculbia carcini, with tlie tnft of clinging roots which it inserts into the hody 

 of its host; 6, its larva (Kauplius) ; o, Tlwmpsonia globosa (Kossmann) ; d,iia larva, 

 Cypris stage. 



which they live, in addition to those which arise from the mere 

 quality and quantity of the nourishment required. 



The peculiar mode of taking up nourishment exhibited by 

 various Parasites must also be shortly described. Asa rule, 

 almost without exception, the larvM of parasites swim or move 

 freely about in water (leading a very unfitly termed active life). 

 During this stage of free locomotion the larvse are usually high 

 in the scale of structure. The larva of the parasitical Copepoda 

 or Cirrhipedia (for inst.i,nce, of a, Sacculina, fig. 1 2) is known 



