16 CRUSTACEA OF ALABAMA. 



quadrangular in outline, the outer of the terminal setae being a short spine, shorter than 

 the stylet. The setae may or may not be webbed. The egg sacs are appressed and 

 contain four or five eggs in the first state and a few more in the post-imago. The eggs 

 are relatively larger than in most species, though as a rule small species have eggs a lit- 

 tle smaller than those of larger forms. The two dimorphic states are very evident in this 

 species as already hinted and are found to depend in part at least upon the habitat. 

 The colors are frequently brilliant, varying from a deep indigo- blue to greenish and 

 brownish. The coloring matter is distributed rather irregularly, but is usually deepest 

 between the bases of the feet, toward the end of the antennae and in the last segment of 

 the abdomen. Males of this species are even more slender, measuring .75 mm., the ab- 

 domen being .28 mm., stylets .06, first thoracic segment about .28 mm., and the longest 

 caudal seta .24 mm. The antennae are long and so curiously geniculated as to resemble 

 the antennae of calanidae. The abdomen in young specimens, before the segmentation is 

 perfect, often appears very long, and it often happens that the fourth pair of feet are still 

 2-jointed in oviferous females. 



Cyclops DiaphanUS, Fischer 1 



(Plate VII, Fig. 3, 



Description of the Female. The body, not including the caudal' setae, measures from 

 .65 to .80 mm. The following are measurements of a rather small specimen ; first seg- 

 ment of cephalothorax .24 second segment .068, third segment .060, fourth segment 

 .036 mm ; the remainder of the body to the stylets measures .24 mm ; while the stylets 

 themselves are .024 mm. long and bear a lateral spine about one-third their length from 

 the apex. The longest seta is .24 mm. long, the outer median seta being about .19 mm. 

 The body is comparatively rather slender and tapering, with an unusually long first thor- 

 acic segment. (Measurements of a large specimen of this species may serve to indicate 

 the observed fluctuation in size: Length .81 mm., thorax .50, abdomen 31, stylets .06, 

 longest seta .40, outer median seta .36 mm.) The antennae are considerably shorter 

 than the first thoracic segment, being about .19 mm. long, the seventh and eighth joints 

 about equal and the longest of the eleven segments. The first joint is very large. The 

 antennae in a state of rest assume a curved position. The antennules are small, the ter- 

 minal segment measuring (in the animal first above referred to) .032 mm. The labrum 

 has six similar teeth which are bordered on either side by a larger one. The longest 

 joint of the outer maxilliped measures .06 mm. All the feet are usually two-jointed in 

 both rami. The outer ramus of the first pair of feet has the terminal joint armed exter- 

 nally with three stout spines, terminally with two setae, and internally with three setae. 

 The second and third pairs of feet are alike in their spinous armature, the outer side of 

 the terminal segment bearing three spines, the end a very large toothed spine and a 

 seta, and the inside four setae. The fourth foot has two spines on the outside of the ter- 

 minal joint, a heavy spine and a seta terminally, and four setae within, while the terminal 

 joint of the inner ramus bears externally one spine, apically a short spine and a seta, 



