STATE GEOLOGIST, 93 



equaling or exceeding: the remaining three. The superior antennae vary in 

 length and form. Their shape is that of a letter s. In the male both antennae 

 possess the hinge, or geniculating joint, which serves as a hand for retaining the 

 female durmg copulation. The antennae are about twenty-six jointed, and fur- 

 nished with numerous setae. The secondary antennae are four-jointed, and have 

 six setae at the end, serving as organs of prehension. 



The mandibles are ovoid bodies, terminating in short teeth, and carrying a sort 

 of palpus o± two filaments. 



The maxillipeds are somewhat similar but are furnished with two toothed 

 processes. 



The first paor of feet are organs of prehension, having two rami, of which the 

 smaller, a three-jointed organ, springs from the base of the outer or main branch. 

 The basal joint of the outer ramus besides bearing the other has two projec- 

 tions on the mner side, the second joint is hook-shaped, as is the final and small- 

 est segment which springs from it. The four following pairs of feet are composed 

 of two rami, each consisting of three setae-bearing joints, as see plate of Cyclops. 

 There is also a pair of appendages at the base of the first segment of the abdo- 

 men. The abdomen is six-jointed, the final joint somewhat bifid, each side 

 terminating in a caudal stylet between which is located the anus. 



These stylets give rise to two small setae on the outer margin and four at the 

 extremity. The inner pair of filaments are usually much the longest, and are 

 also diflierent from the others in having a joint near the base which gives greater 

 freedom to their motions. The seto are usually barbed backward, and in old 

 individuals are most beautifully pectinate. In cases where the moulting has been 

 arrested these and the other hairs attain a curiously long growth, as illustrated 

 in the plate, and the barblets become filiform appendages. 



The digestive canal begins near the front of the thorax and can be traced to 

 the anus. The ovaries are two, and are easily seen in the body, and communicate 

 with external ova sacs. After the eggs are extruded from the ovary into the 

 pouches they are not dependent on the mother, but will come to maturity if 

 separated from her. These eggs vary in number, old individuals laying upwards 

 of forty. It is calculated that in one year a single female would have becouce 

 the projenitor of 4,442,189,120 young so that the abundance in which they occur, 

 notwithstanding the ravages of the Hydrae, and other enemies, is not strange. 

 A single copulation fertilizes the female for life, as in the case of the Aphides. 

 The eggs, as they are hatched, descend from the ovary covered by a transparent 

 pellicle in which they remain from two to ten days. The growth of the young 

 is illustrated in the plate, the operation occupying about twenty or thirty days. 

 The Cyclops moults a number to times during its life, and i as the power of 

 replacing lost parts, they are also very tenacious of life, often reviving after being 

 frozen lor a long tirr.e in the mud and water, which form their hiding places. 

 The cyclop . is probably both carniverous and a vegetable feeder. 

 Plate III. represents the usual form, the figures showing the diff'erent stages 

 are copied from Dr. Baird's Entomostraca. Plate IV. gives one of the varieties 

 collected here which may be worthy of a specific name; the greatly exaggerated 

 caudal filaments and general hairiness is, however, only an age-modification, the 

 color of this vanety is dark, while the eggs in the sacs are pelJucid. Another 

 variety is oblong in shape and lighter in color, while the e^g sacs are opaque. 

 Still other varieties are smaller, and vary from bright red to green in color, hav- 

 ing the egg sacs diverging from the abdomen. There seem to be intermediate 

 forms and it is best to await further study before separating these varieties. 

 (See Plates III. and IV.) 



