CAUSES OF VARIATION 



2. If two or if three segments be cut off, an equal number will 

 be restored (see Fig. 36, C, D). 



3. If four or five be cut off, generally, but not always, a corre- 

 sponding number come back (see Fig. 36, E, F). 



i 



B 



G 



FIG. 35. The method of growth in regeneration 



A, tail of Fundulus heteroclitus : cut squarely, it regenerates as at B ; cut obliquely, as at C. 

 In D and E are shown regeneration from two oblique cuts ; G, tail of stenopus, regen- 

 erating from square cut at //and from oblique cut at /. After Morgan 



4. If six or more be cut off, only four or five come back. 

 These are the segments constituting the head proper, all of which 

 are restored ; but if the cut be made farther back, the intermediate 



