78 INVERTEBRATE ZOOLOGY 
formed opens into the genital cloaca. This structure, which thus 
receives all the ducts from the genital glands, communicates 
with the outside through the genital pore, a median, ventral 
opening in the hinder part of the body. 
Exercise 3. Draw a large outline of the animal and place in it as 
much of the reproductive system as you have observed. 
The nervous system. Beneath the eye-spots will be seen the 
opaque brain, a large nervous mass consisting of a pair of minor 
masses united by a broad commissure. From its anterior and 
lateral sides numerous sensory nerves pass to the anterior body- 
surface, which render this extremity a highly sensitive tactile 
organ. From its posterior side a ‘pair of large longitudinal nerve 
cords passes to the hinder end of the body, being united at 
intervals by transverse nerves. 
The excretory system. ‘This consists of a system of minute 
tubes which extend throughout the body and collect the excrete 
matters from the tissues. There are two main longitudinal tubes 
extending the length of the body, which open to the outside 
through minute pores on the dorsal surface of the animal. 
These tubes are not straight but coiled and give off numerous 
branches, at the termination of each of which is a peculiar cell 
with a vibratory process at its base called a flame cell; they are 
joined by a transverse tube at the anterior end of the animal. 
Portions of the excretory system can often be seen in the com- 
pressed animal, where they appear as fine lines. 
Exercise 4. Draw an outline of the animal and place in it as 
much of the nervous and the excretory system as you 
have observed. 
No special respiratory system is present in the Turbellaria, 
the ciliated outer surface of the body performing this function. 
A circulatory system and a blood fluid are also wanting. The 
branching of the digestive and excretory systems is correlated 
