440 T. H. MORGAN. 



We see that the right and left sides of the arm vary independ- 

 ently, so that each forms its half-coloured band. In the 

 present case something has disturbed the regularity of the 

 process, so that the colour has appeared too soon on the right 

 side, as the figure shows. 



In fig. 98 we have a somewhat similar case. Here the half- 

 bands are separated by an entire uncoloured segment. In 

 other cases that I have seen the half-bands may be even 

 farther separated by uncoloured segments. 



From a study of these and similar variations we find that 

 the following relations exist. When a segment is only half 

 coloured on one side it is generally, though not invariably, 

 followed, sooner or later, by a segment coloured only on the 

 opposite side. We might say that the colour-ring had split, 

 and its two halves had appeared on different segments, so that 

 when we find a half-baud on the right we would expect to find 

 its other half on the left, and vice versa. 



When half-bands appear, one of the halves seems always to 

 come in too soon proximally. The other half then appears on 

 its normal segment or beyond it. 



My material has been too limited to warrant any attempt at 

 further explanation of the phenomenon, and no doubt a more 

 extensive study would show exceptions to these statements 

 that would render an explanation still more difficult. 



The three following tabulations of the colour-bands show the 

 main variations that come in. The x indicates a coloured ring. 

 The figures between these indicate the number of uncoloured 

 segments. The half-coloured bands are indicated by x L. ^ and 

 X 5 R., depending whether the colour is on the left or right 

 side of the arm as looked at from below. 



