STRUCTURE AND DEVELOPMENTAL RATE 203 



twisted tubular shape. The small figure immediately below the 

 defective head represents the opposite view of this head. 



In figure 16 the smaller component presents a typical Cyclopean 

 eye beneath the anterior tip of a narrow, almost solid brain. 

 Here again the mouth and gill structures are grossly deformed. 



Finally, figure 17 shows only an amorphous mass representing 

 the smaller head on a perfectly normal larger component. This 

 head mass contained no ophthalmic structures at all, the brain 

 was entirely distorted and the mouth* was completely absent, 

 with the gill structures greatly deformed. Behind this head mass 

 the pectoral fins were fairly developed and a short anterior body 

 portion representing the rest of the component is shown in the 

 figure. 



Figures 18 and 19 give two views of the only case observed 

 among these individuals in which the larger component was 

 also deformed. In figure 18 the larger left head is seen, in dorsal 

 view, to have a left eye, but no right. The ventral view shown 

 in figure 19 illustrates the normal left eye and also shows the 

 normally well-formed mouth and gill arrangements in the superior 

 component. The right head, or smaller component, is shown 

 from both views to be much more decidedly deformed than the 

 left. It is completely anophthalmic and the brain, mouth, and 

 gill structures are clearly abnormal. 



Since in all the other specimens the larger component is normal, 

 we may claim with justification that the larger component in 

 this specimen simply happens to be deformed as any single 

 individual might chance to be. But the smaller component is 

 more decidedly deformed than the larger, and the deformity in 

 this instance no doubt results from the same reasons which have 

 brought about similar deformities in all other smaller components 

 of the entire group of double specimens studied. It is only to be 

 expected that the larger component developing under somewhat 

 modified conditions, such as those necessary to induce the initial 

 doubleness, will occasionally be further affected and present 

 some structural deficiency. Such abnormalities are not uncom- 

 mon among those members of the experimental group which are 

 not induced to double formations, but continue to develop as single 



