THE SPACE 



FACTOR AND THE RATE OF 

 DIFFERENTIATION 



GROWTH AND 



PUBPOSE : To determine the relation of the single factor of space (lebensraum) to the rate 

 of growth and differentiation of the tadpole. 



MATERIAIS: 



Biological : Chmlating female, and males of Eana plplens (or any Anuran) . 



Technical : Slate bottom aquaria measuring 12 x 2h x ^ Inches, auh-dlvided hy flne- 

 meshed wire (galvanized) screen Into 6 compartments measuring Q x 6 x h 

 Inches. The screen may he held In place by paraffin, permoplaat, or silt 

 rubber tubing. The purpose is to provide free circulation of food, 

 respiratory gases, and waste matter throughout the entire aquarium. The 

 medium and all faecal material must be drained off by siphoning at in- 

 creasingly frequent Intervals as development progresses. (Other types of 

 aquaria, such as enamel pans, can be adapted to this experiment.) 



METHOD: 



Precautions : 



1. Make the compartments escape-tight, so that swimming tadpoles cannot move from 

 one compartment to another. Wire mesh must have smaller holes than the diameter 

 of the eggs used. 



2. With some crowding. It will become increasingly important to change the medium 

 frequently. A gauze-covered siphon tube may be used to remove the water, but 

 when the faecal matter is abundant. It may be necessary to remove the tadpoles 

 from a compartment and use the uncovered siphon. Remove dead animals immediate- 



Control : The variations in numbers in the different compartments will include what may 

 be considered the control, i.e., that compartment in which there is maximum or most 

 rapid growth. 



Procedure : 



1. Ovulate the female in the usual manner, fertilize the eggs and allow them to 

 cleave. At the 2-cell stage remove eggs from the cluster and place them in 

 groups of no more than 5 In each of the compartments, the total number per com- 

 partment being indicated in the diagram below. 



^ 



-2k"- 



-> 



12" 



^wlre screen 



h" deep 



(♦Number of animals per compartment) 



-1U6- 



