44 



I -I III R F. HYRM--. 



EXPLANATION OF PLATE I. 



Cyclops signatus var. tenuicornis. (Cyclops signatus var. annnlicornis; C. albiilus 



Jurine.) 



FIG. i. The inner ramus of the fourth swimming foot of an adult female, 

 showing the small distal seta. 



FIG. 2. The fifth foot of an adult female, showing the characteristic basal 

 joint of the variety C. signatus tenuicornis. 



FIGS. 3, 4, 5 and 6. The fourth swimming feet of young in the sixth stage of 

 the metamorphosis, showing the characteristic small distal seta. 



FIGS. 7, 8 and 9. The fourth swimming feet of young C. Icnuicornis, sister 

 forms of 3, 4, 5 and 6. The distal seta is wholly wanting. The location of the 

 seta is indicated by a notch in the chitin. 



FIG. 10. The inner ramus of the fourth swimming foot of an adult female. 



FIGS, ii and 12. Two young of Fig. 10. The sixth stage of the metamorphosis 

 is shown in Fig. n. Fig. 12 shows the fourth foot in the seventh stage. 



The adult female, Fig. i, was isolated July 28. The young of this female (Figs. 

 3 to 9 inclusive) were studied August 10. The sixth stage of the metamorphosis 

 was, therefore, reached inside of two weeks. 



