286 



AQUATIC MICROSCOPY FOR BEGINNERS. 



d. Ventral plates oval, with an oval plate on each 

 side; mouth round, with a circular hood. Ar- 

 renjirus, 5. 



d. Ventral plates narrow, curved, each with two or 



three translucent tubercles. Atax, 6. 



e. Eyes four, on a lanceolate plate; coxae in four 



groups. Limndchares, 7. 



I. The Water-bear: Macrobidtus (Fig. 192). 



The body is soft, colorless, and transparent. The 

 legs are very short, and have on the end of each sev- 

 eral sharp claws, the legs being arranged three on each 

 side of the body and two at or near the posterior ex- 

 tremity. The mouth is a small opening 

 at the front of the part representing the 

 head, and is followed internally by two 

 short, somewhat curved, diverging rods, 

 said to be used to wound the prey. 

 The so-called gizzard, at a short dis- 

 tance from the mouth, is plainly visible 

 through the transparent body. It has 

 no motion. -Two small eyes are usually 

 present, one on each side of the head. 

 The animal's movements are exceedingly 

 slow and awkward, the creature appear- 

 ing to work hard, with but little result so far as 

 progress is concerned. 



Macrobidtus is produced by eggs, which are deposited 

 in an interesting way. When they are suiSciently 

 matured, the water-bear sheds its skin and leaves the 

 eggs in the empty and cast-off case. It is no unusual 

 occurrence to find the empty skin of Macrobiotus with 

 the empty eggs inside, the young having escaped. 



Fig. ig5. — The 

 Water-bear 

 (Macrobi6tus). 



