256 ZOOLOGY 
The head bears a large median compound eye, which is 
formed by the fusion of two originally lateral eyes, and behind 
this lies a single simple eye. 
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oe 
| MI 
As A2 
Fic. 153.—Side view of female of Daphnia similis. After Claus. 
1. Antennules. 9. Heart. 
2. Antennae. 10. Brood pouch. 
3. 1st pair of legs. 11. Shell gland. 
4, 2nd pair of legs. Th. 3 and Th. 5. 8rd and 5th thoracic 
5. 3rd pair of legs. segments. 
6. 4th pair of legs. A.1, A.2, A.3. Ist to 38rd abdominal 
7. 5th pair of legs. segments. 
8. Hepatic diverticulum. 
An upper lip guards the entrance to the alimentary canal, 
and the mouth lies between the two-toothed mandibles; the 
