PROTOPLASM AND SIMPLE ANIMAL FUNCTIONS 



465 



FIG. 257 



drawings of Tubifex, if possible, showing any interesting structures to 

 be seen in the animal. 



Expt. 10. Cyclops is one of many genera of the Crustaceans which 

 inhabit stagnant waters both fresh and salt. Note the general shape of 

 the animal, and his antennae in 

 front with which he jumpingly 

 swims rapidly through the water. 

 Study the prominent alimentary 

 canal (a yellow mass in the 

 middle line) and its peristaltic 

 surging back and forth. Note 

 the single eye, a spot of pig- 

 ment, above and in front. Note 

 the symmetrical masses of eggs 

 or of embryos which the females 

 carry about, one mass on either 

 side. 



Expt. 11. Tardigrade is used 

 as a type of the animals which 

 survive the dried and hibernat- 

 ing condition. Two-day demon- 

 stration of revival after drying. 

 (See Fig. 129 and its legend.) 



Daphnia (Expts. 12 to 19). 

 The last of the microscopic 

 animals we may study at present 

 is Daphnia, a fresh- water clado- 

 ceran crustacean of great value 

 and interest in physiology be- 

 cause of its extreme transpar- 

 ency combined with a relatively 

 high complexity of development. 

 The animal is to be studied flat 

 on a slide with water too small 

 in amount to allow of its jump- 

 ing about. Note (1) the general 

 striking effect of movement in 

 every part of the animal at once ; 

 (2) the conspicuous heart, and 

 the blood-corpuscles circulating 

 over the body; (3) the single but 

 compound eye, composed of omatidia (single eyes) ; (4) the eye-muscles 

 in constant action; (5) the brain; (6) the alimentary canal with its 

 surging yellow-green contents and its movements of peristalsis; (7) 

 the gill-feet; (8) the brood-sack and its probable embryos in some stage 

 of development from mere eggs to forms almost like their mother; (9) 

 the antennae with which it jumps in a characteristic manner through the 

 30 



Parts of Daphnia pulex, De Geer: a, the an- 

 tennule of the male; b, maxilla; c, the first "gill- 

 foot" of the female; c' , the same of the male; d, 

 one of the second pair of gill-feet; Br, respiratory 

 sac; Ex, exopodite. (Glaus.) 



