152 W. K. BROOKS. 



descendants of ordinary swimming copepods, and not of phyllo- 

 pods, and there is no reason for holding that the copepodan type 

 itself is degenerate, except the supposed exigencies of morpho- 

 logical philosophy. 



The active locomotor habits of the eucopepods of the open 

 ocean would seem to be conducive to advancement rather than to 

 degeneration, and the occurrence of phyllopods in the lower Cam- 

 brian is, of course, no more evidence that they are primitive 

 Crustacea than the occurrence of pteropods and gasteropods is that 

 they are primitive molluscs. 



I am unable to see any valid objection to the view that the 

 copepods are primitively pelagic ; that they have been evolved at 

 the surface of the ocean from pelagic nauplii, and that the great 

 group Crustacea has been derived from them. 



We have already seen that the eucopepods are the chief inter- 

 mediary between the micro-organisms of the ocean and the larger 

 and higher marine animals ; that they prey upon the protophytes 

 and protozoa, and in their turn supply either directly or indirectly 

 most of the food for the large inhabitants of the water ; that most 

 pelagic larvffi feed upon theth ; that they are the food of the great 

 pelagic banks of pteropods and heteropods, of many coelenterates, 

 of the young of most fishes, and of some of the most abundant 

 and important adult fishes, like the herring, and that the sea-birds, 

 the cetacea, and in fact almost all of the larger pelagic animals, 

 prey upon animals which in their turn prey upon copepods. 



The animals which are most important at one period in the 

 earth's history are often replaced by others at another period, and 

 it is, of course, possible that the modern copepods now fill a place 

 which was in former times filled by something else ; but as their 

 organization, as compared with that of the other Crustacea, exhibits 

 all the characteristics of a jn-imitive pelagic stem-form, and inas- 

 much as the remains of animals, like the pteropods, which now 

 live almost entirely upon copepods, are found in the oldest fossili- 

 ferous rocks, there is every reason to believe that the group formed 

 an important constituent of the primitive pelagic fauna. 



No one who advocates at one time the morphological heresies 

 which are involved in the view that appendicularia is a stem-form 

 which is pelagic in its origin ; that the nauplius is a persistent 



