132 THE BIOLOGY OF THE ANIMAL 



forceps pull out one of the " hearts " in such a 

 way as to prevent the blood escaping from the 

 part included between the two forceps. Place 

 this piece of the blood-vessel on a slide, put on a 

 cover-glass, and examine immediately under a 

 high power. What is the color of the blood ? 

 ITote .the serum and the corpuscles. Are the 

 latter colored ? To what is the color of the blood 

 due ? Compare with the frog's blood in this re- 

 spect. What differences between the corpuscles 

 found in the blood and those found in the peri- 

 visceral fluid ? Put a drop on the slide, but do 

 not cover. Does the blood coagulate ? 

 Draw some of the blood corpuscles. 

 Remove the alimentary canal from the pharynx to 

 the posterior end. 



0. The Nervous System. 



Lying in front of the pharynx find 



a. The supra-CBSophageal ganglia or "brain." 



— What is their position? Shape? Are they 

 connected ? What is their color ? 



1. The circum - oesophageal commissures or 



"throat-collar." — Position? How are they 

 formed ? What do they connect ? 



c. The ventral nerve - cord. — Position ? How ' 



formed ? How far does it extend ? What is its 

 relation to the intestine ? Eelation to the " throat- 

 collar " ? 



On the ventral nerve-cord look for 



d. The ventral ganglia. — What is their position ? 



Shape? How many in each somite? Look for 

 small nerves running from each ganglion to the 

 body-wall. 



