248 MICROSCOPY FOR BEGINNERS. 



always present at some time of the animal's life. The 

 shell is oval and slightly flattened. The antennae are 

 prominent, and are usually divided into two parts at 

 the free end, each division bearing several feathery 

 bristles. The feet are flattened, and generally in rapid 

 motion, so as to bring food to the mouth, and oxygen 

 to the blood. The heart is noticeable as a small color- 

 less organ under the shell of the back near the head. 

 It pulsates rapidly. The eye is large and conspicuous. 

 The eggs are placed in a brood cavity, as shown in the 

 figure, and there hatched, the young being very different 

 in appearance from the parent. Daphnia is common 

 in the spring. 



2. SCAPHOLEBEUIS. 



The shell is somewhat beaked and usually dark brown. 

 The surface may be indistinctly reticulated or entirely 

 smooth. From jBosmina, for which the beginner may 

 be inclined to mistake it, the absence of the curved, 

 cylindrical antennae common to that species will distin- 

 guish it. The posterior spines are short. The eye is 

 large and conspicuous. The egg is carried in the 

 brood cavity. It is said that but one egg is present at 

 a time. This Entomostracan is common. 



3. BOSMIKA (Fig. 160). 



The student will not have any trouble to recognize 

 6smina, on account of the long, large, cylindrical an- 

 tennae, each one curving downward from the side of 



