10 LABORATORY OUTLINES FOR EMBRYOLOGY 



nucleus in each part? How does the nucleus here differ 

 from the nucleus in the unfertilized egg? 



Draw a two-celled, a four-celled, and an eight-celled 

 stage. Label all the parts. Make each drawing one and 

 one-half inches in diameter. 



(2) Unequal Cleavage 



Examine a frog's egg which has not divided. One 

 part of the egg is dark and the other part is light. The 

 dark part of the egg is the animal pole; the light part is 

 the vegetative pole. Is the pigment confined entirely to 

 one part of the egg? 



Draw a lateral view of an unsegmented egg and label the 

 parts. Make the drawing about an inch and a half in 

 diameter. Shade in the pigmented part. 



Find a two-celled stage. How has the division plane 

 divided the egg with reference to the light and dark 

 portions? Is there any difference in the depth of the 

 segmentation furrows? How do you account for it? 



Draw a two-celled stage, lateral view. Label parts. 



Study a four-celled stage. What is the relation of the 

 second cleavage plane to the first cleavage plane? To 

 the polls of the egg? How do the cells compare in size? 



Draw a four -celled stage, view from the animal pole. 

 Label the parts. 



Study an eight-celled stage. What is the relation of 

 the third cleavage plane to the other two cleavage 

 planes? To the polls of the egg? What is the com- 

 parative size of the cells? 



