162 



ESTHER F. BYRNES. 



ARMATURE OF THE SWIMMING FEET. 



First Foot. 



Outer Ramus. Inner Ranuts. 



3 outer spines. I outer seta. 

 I apical spine. 

 I apical seta. 



4 inner setae. 



I apical spine. 

 I apical seta. 

 5 inner setae. 



Second Foot. 



Outer Ramus. Inner Ramus. 



3 outer spines. I outer seta. 

 I apical spine. 

 I apical seta. 



4 inner setae. 



I apical spine. 

 I apical seta. 

 5 inner setre. 



Third Foot. 



Fourth Foot. 



Older Ramus. 



3 outer spines. 

 I apical spine. 

 I apical seta. 



4 inner seUe. 



Inner Ramus. 

 I outer seta. 

 I apical spine. 

 I apical seta. 

 4 inner setie. 



Outer Ramus. 



3 outer spines. 

 I apical spine. 

 I apical seta. 



4 inner seize. 



Inner Ramus. 



1 outer seta. 



2 apical spines. 



3 inner setae. 



The antenna and fifth foot of this form are seen in Fig. 2. 

 The pravalence of the form alone is not sufficient reason for 



FlG. 2. Shows the antenna and the fifth foot of a Cyclops with nine antennal seg- 

 ments. The fifth foot is two jointed and resembles the fifth foot of the Cyclops with 

 the ten-jointed antennae. 



regarding it as a distinct species, and the probability is that we 

 are here dealing with a transitional stage in the development of 

 a species with a greater number of antennal segments, as seen in 

 the case of the fourteen-jointed form, for no species in its mature 

 condition is recognized as having nine antennal segments, while 

 the fact that the mini arc two-jointed and the number of seta on 

 the last joint of the inner minus is exceptionally large, suggests 

 that the rami may subsequently acquire a third joint. Moreover, 

 the armature of the feet is strikingly like the armature of another 

 Cyclops having ten antennal segments. 



This second form which occurs frequently in the same locality, 



