42 ESTHER F. BYRNES. 



The best results in rearing the young were obtained when the 

 water used in the aquaria was the filtered water from the pond 

 in which the cyclops had been collected. After having set up 

 aquaria with water from various sources, this method was relied 

 on as the one which insured least loss of time through high 

 mortality. 



EXPLANATION OF PLATES. 



Plate I. shows the inner ramus of the fourth swimming foot of 

 an adult female, C. signatus var. tenuicornis and the correspond- 

 ing ramus in each of her seven young. The rami are unseg- 

 mented and the armature is incomplete, but the distal seta pre- 

 sents its adult characteristics. In four of the sister forms the 

 seta is present but minute. In three of the young it is altogether 

 wanting though its position is indicated by a notch in the chitin. 



Fig. 10 of Plate I. shows the inner ramus of another adult 

 female with the small seta. Figs. II and 12 show the corre- 

 sponding rami in two of her brood. At the time the studies were 

 made the remaining young of this set had not reached the stage 

 in which the fourth foot develops. 



Plate II. shows the young of a brood in which some young are 

 in the sixth stage, i. e., with nine antennal segments, some in 

 the seventh stage with ten antennal segments and all the rami 

 two-jointed, while still others are in the eighth stage of the meta- 

 morphosis having three joints in the rami of the swimming feet. 

 All of the individuals of all of the successive stages show the seta 

 in question to be strikingly reduced. 



We are evidently dealing here with a constant character which 

 appears in a relatively early stage of a complicated metamor- 

 phosis and retains its peculiarity in all subsequent stages and 

 even remains as one of the recognition features of the adult. 



Similar experiments were made in rearing the young of C. 

 signatus var. coronatus in which all of the setae attain a marked 

 development. 



Plate III. shows the inner ramus of the fourth swimming foot 

 of an adult female C. signatus var. coronatus. The distal seta is 

 large and well developed. The young are like the female parent 

 in their armature. Moreover, the- hairiness of this Cyclops is 

 not an indication of age, but an inherited character for the 



