HETEROGENV AND VARIATION IN COPEPODA. 



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combines the following characteristics : Antennce tcn-jointcd ; 

 raini of swimming feet t-ivo-jointcd ; rudimentary fiftli foot two- 

 jointed. 



ARMATURE OF THE SWIMMING FEET. 



3 outer spines. 



2 apical spines. 



3 inner setae. 



First Foot. 



Outer Ramus. Inner Rattnts. 



I outer seta. 

 I apical spine. 

 I apical seta. 

 5 inner setae. 



Third Foot. 

 Outer Raimis. Inner Ramus. 



3 outer spines. I outer seta. 



I apical spine. I apical spine. 



I apical seta. I apical seta. 



4 inner setae. 4 inner sete. 



Second Foot. 

 Outer Ramus. Inner Ramus. 



3 outer spines. 

 I apical spine. 

 I apical seta. 



4 inner setae. 



i outer seta. 

 I apical spine. 

 I apical seta. 

 5 inner setae. 



Fourth Foot. 

 Outer Ramus. Inner Ramus. 



3 outer spines. I outer seta. 



I apical spine. I apical spine. 

 I apical seta. I apical seta. 



4 inner setae. 3 inner setce. 



FIG. 3. The antennae, the abdomen and caudal stylets and the two types of fifth 

 foot correlated with the lo-jointed antenna;. C shows the fifth foot correlated also 

 with the 9-jointed antennae, while D shows the fifth foot correlated with the II- 

 jointed antennas. B represents the type of abdomen and stylets correlated with 10 

 antennal segments irrespective of the form of the fifth foot. 



Wherever these forms with the nine- and ten-jointed antennae 

 occur they show the same striking similarity in the armature of 

 the swimming feet. The nine-jointed forms are perfectly constant 



