STRUCTURE AND DEVELOPMENTAL RATE 205 



In figure 21 the lower component is somewhat smaller than 

 the upper and there is a complete absence of one eye. A drawing 

 of the opposite side of this head shown below figure 21 represents 

 the other eye with an extreme coloboma, its entire ventral part 

 being deficient. This component seems otherwise normal. 



Two views of another double individual are illustrated by 

 figures 22 and 23. The larger component is perfectly normal 

 except for the fact that its tail is somewhat unusually bent. 

 The smaller component is completely anophthalmic and its 

 brain presents a very abnormal contour. 



In figure 24 the smaller component is still more reduced in 

 size as compared with the larger normal member. Here also 

 the extent of deformity is still more marked than in the two 

 foregoing specimens. There is one small deeply buried eye in 

 a more or less shapeless head. The mouth and gills are dis- 

 torted and poorly developed and the brain is deformed. The 

 body is small and abnormally developed. 



The specimen shown in figure 25 carries the condition a step 

 further. A normal well-formed trout has attached to its ventral 

 surface a greatly coiled and twisted twin. This small component 

 shows a minute almost buried eye, E, and the head is in many 

 ways, grossly deformed. But for the extreme coiling, the body 

 would present almost as good an appearance as that of the smaller 

 component in figure 24. 



In figure 26 the small twin has a still more malformed head 

 with no eye, but a more or less anteriorly protruding crystalline 

 lens just beneath the skin. The body here is shorter than in 

 the figure above and has only a single twist. 



Finally, in figure 27, the last of the series, the large component 

 is a splendidly developed young fish with little more than a nodu- 

 lar twin attached to the ventral portion of its yolk-sac. The 

 little component has one small eye deficient ventrally, no external 

 mouth or branchial formations, the brain is tubular and the entire 

 head knob-like in shape. The middle body portions are sup- 

 pressed and only a conical stump-like tail end is shown. The 

 entire growth of the lesser component has been but a small 

 fraction of that attained by the larger member. One might 



