1 879 ] Fresh- 1 1 'atcr litit<>inostraca. 62 1 



Iciruch' into tlic diet of fish, oven of the laiLJ^ r wirieties. The 

 ]ar(;ci' portion of tlie I^ntoinostr.ic.i, nuineric.ill)' at least, are 

 vegetable feeders and live on the minute particles of matter float- 

 incf in the water, which otherwise would tend to render our waters 

 impure. The snails wipe clean the stones and water-plants, and 

 the scaveni^er fishes remove the carrion, but it remains for minuter 

 forms to search carefully each drop and remove the particles, 

 microscopic even to the thousand eyes of the dragon-fly larva. 

 Thus the Sida (Plate in) in swimming uses the branchial feet 

 within the shell-valves, not onl\^ in taking the necessary air from 

 the water, but, by creating a counter current between the bases of 

 the feet, particles of food are constantly brought within reach of 

 the jaws. In common with low forms of animals in general, the 

 processes of reproduction are often curiously anomalous. Con- 

 gress of the sexes is in many cases unnecessary for many genera- 

 tions, and some forms, especially the Artcmia, or " brine shrimp," 

 seem unusually susceptible to changes in their environment. 

 Males are often produced only in certain seasons of the year or 

 under certain climatic conditions. 



In the Daphnia the females produce young by simple budding 

 from the ovary, but in the winter the ovum is enclosed between 

 the valves of the carapace, which is removed at each molt, and it 

 is thus enabled to resist the severity of the cold season. Speaking 

 of the molt it is interesting to note that every hair, even to the 

 finest filament, throws off a sheath, so that the cast-off integu- 

 ment is a perfect copy of the animal from which it came. In the 

 higher forms the eggs are carried during the later stages of em- 

 bryonic existence in double or single sacs extending beneath or 

 on either side of the abdomen. In the Daphnia and other forms 

 enclosed in a carapace the animal is oviparous, and the young 

 can be seen within the shell in a cavity above the abdomen for 

 some time before they are sent out to paddle their own crystal 

 canoe. They may be remo\'ed from the parent without inconve- 

 nience. In the larger sub-division, the Lophyyopoda, the chief 

 organs of locomotion are one or both pairs of antenna,', though 

 natatorial feet are never wanting. The antenn;e also serve a.s pre- 

 hensile organs in the Cyclopoidca, while the feet throughout the 

 whole legion have branchial filaments. 



Every one who has used thj microscope has met with some of 

 these animals, and we will mention a few forms. If water, taken 

 from the clear surface* of a lakr (M1 a siiiinx' day, be carefull\' ob- 



