DAPHNIA 57 
phyllopod), in which we can recognize the basal protopodite 
and two broad terminal pieces, the endopodite and exopodite. 
The short abdomen articulates with the thorax and is bent 
beneath it, where it may be seen often moving rapidly back 
and forth. 
Exercise 1. Draw an outline of a side view of the animal on 
a large scale and label the appendages and other parts 
observed. 
Exercise 2. Draw a highly magnified view of one of the thoracic 
appendages and label accurately all the parts. 
Internal organs. The digestive tract passes from the mouth, 
which is ventrally placed and lies back of the ventral cleft in 
the shell, first forward, then turns dorsally and finally posteri- 
orly and extends back to the anus near the end of the abdomen. 
Near the anterior bend of the digestive tract a pair of colored, 
curved pouches communicate with it; they are liver-sacs. The 
sac-like heart may be seen beating rapidly above the intestine. 
It possesses a pair of lateral openings into which the blood 
streams from the body-cavity with each dilation, and an ante- 
rior opening through which it is sent into the forward part of 
the body with each contraction. There are no other blood 
vessels. Below the heart is a pair of excretory glands, called 
the shell glands, which open to the exterior near the mouth. 
The nervous system consists of an optic ganglion and a brain, lying 
back of the eye, and a ventral nerve containing seven ganglia. 
The reproductive organs. The daphnias which are usually seen 
are all parthenogenetic females, the males making their appear- 
ance at certain times of the year only. The female animal is 
larger than the male, and may be distinguished by its brood-sac. 
This is a large space just beneath the dorsal wall of the thorax 
in which the eggs and the young brood are carried. The ovaries 
are a pair of tubular organs alongside the intestine, which com- 
municate, by means of short oviducts, with the brood-sac. The 
