ORDER COPEPODA. 



The minute animals which constitute this order are nearest like the extinct Euryp- 

 teridce of Carboniferous times, but never attain the size of these archetypal Crustacea. 

 They are essentially active, natatory creatures, swimming by means of long, many-joint- 

 ed antennae, but also provided with at least four pairs of functional legs and a fifth pair 

 generally modified to support the egg-sacs or to function in the act of fertilization. In 

 the male the antenna? and often the feet are hinged or dactylate, for prehension. Al- 

 though, as above indicated, the majority of the order are free-swimming and very active, 

 a considerable number have adapted their structure to a parasitic life upon the gills of 

 fishes or other Crustacea, while still others are strangely modified in accommodation to 

 the conditions of abysmal or limous situations. No group of microscopic organisms is 

 more generally available or interesting for study. Without repeating general structural 

 descriptions to be found in special monographs, we may simply notice that the non-para- 

 sitic division or gnathostoma fall naturally into six families, of which four have been noted 

 in Alabama, as well as representatives of two families in the Pcecilosto7na or semi-para- 

 sitic group. 



FAMILY CALANID/E. 



This family is typically pelagic, the whole structure being adapted to a life in open 

 bodies of water, as seen in the slender natatory form, long antennae, and graceful move- 

 ments. The species are found in great numbers in the open seas, irom the equator to 

 the poles and the geographical range of many species is enormous. There are, how- 

 ever, a few genera to be found in inland or littoral locations, but generally these bear 

 evidence of being out of their habitat in the compacted or stunted body and appendages. 

 The females of this family carry the eggs in sacs beneath the body and the young are 

 hatched as curious, six-limbed nauplii of oval form, which are at once exceedingly active. 

 Body consisting of from ten to twelve (obvious) segments ; abdomen slender, bearing 

 two cylindrical stylets ; anterior antennae, with twenty-five segments, as long at least as 

 the thorax ; antennules bi-ramose, inner ramus multi-articulate ; mandibles with seven to 

 eight teeth and furnished with a bi-ramose palp ; second maxillipeds long, many-jointed, 

 directed forward, armed with a brush of strong setae ; first four pairs of feet bi-ramose, 

 typically with three segments in each ramus ; fifth pair frequently very different, sexual- 

 ly functional; ova enclosed in a single sac beneath the abdomen. The principal genera 



