4.22 Harris Hawthorne Wilder 



since before that event such embryos are usually symmetrical and unde- 

 formed, while the turning of each of the two components causes a 

 mechanical interference of parts and components that utterly destroys 

 the natural symmetry [Kaestnee] . 



With the exception of the everted brain and the correlated changes 

 in the adjacent parts, Teras XII, the monster in question, is symmetrical 

 and perfect, that is, it is cosmobion. Each component has both outer 

 and inner eyes, but the axial divergence of the two components is so 

 much less than in the previous case, Teras I, that there is no longer room 

 for the independent expression of the two inner eyeballs, and they there- 

 fore develop in the form of a double organ, of abnormal width but per- 

 fectly symmetrical in all details. The palpebral opening is single, but 

 bent in the form of a U, suggesting its compound nature. 



In other points this specimen is very much like the preceding. There 

 are two snouts, diverging laterally from the median plane of the monster 

 at an equal angle, and the two lateral sides, with their eyes, are normal 

 in every respect. Upon the ventral side of the head each component is 

 s.een to be possessed of the characteristic sub-mental wart with its tuft of 

 bristles; these plainly mark the mid- ventral line of each, and thus their 

 distance from each other shows the amount of the divergence of the two 

 components at this level. There is also a cylindrical papilla of unknown 

 significance, which projects from the inner angle of each mouth. Its 

 external surface is covered with hair-bearing integument, giving the 

 suggestion that it is a detached piece of the lower lip, but it takes its 

 origin, not merely from the edge of the gum, but from the surface of the 

 hard palate nearly to the median line. 



In describing the compound median eyeball, it seems best to consider 

 first the eyeball itself, both externally and internally, with its associated 

 parts other than the muscles, and then these latter, the determination of 

 which must rest in part upon the relations of the eyeball. 



The compound eyeball, which consists of the left one of A and the 

 right one of B, is of a flattened pyriform shape, and in its lateral diam- 

 eter is nearly double the normal width. Along the dorsal and ventral 

 middle lines it is slightly grooved, suggesting its double nature. It is 

 supplied with two optic nerves, which converge from the two sides and 

 enter the eyeball normally and quite near together. Beneath each eye- 

 ball component, and lying a little to the inner side, is a large glandular 

 mass, which is evidently the Harderian gland, an organ always large in 

 the pig. 



