The Morphology of Cosmobia 423 



The eyeball was dissected by dividing it in two horizontally and then 

 lifting up the dorsal half. The condition thus found is shown in dia- 

 grammatic form in Fig. 31. Here the key to the situation is found 

 in the iris, or rather irides, which by their position express the general 

 relationships. There are two of these, each forming a complete ring 

 as normally, but they are united along their inner edges for about half 

 their circumference, leaving the remainder free and divergent. It will thus 

 be seen that there are two distinct pupils, as indicated by the two arrows, 

 and that these look forwards and towards one another and open into a 

 common aqueous chamber which is covered in front by a common cornea 

 of an oval shape. Each iris ring contains a crystalline lens, which is con- 

 siderably larger than the diagram, so that in reality the two lenses 



Optic Nerves 



Fig. 31. DiajiraiHinatic view uf the inedian double eye of Terns XII. Tbe 

 two pupils are formed by tbe apertures through which pass the two arrows, 

 and thus open into a common anterior chamber. 



were in close contact with each other and nearly filled the pupillar 

 orifices. At the point of contact each lens originally displayed a small 

 flat facet, formed by the pressure of the other lens, but there was 

 absolutely no organic connection between the two. The two lenses were 

 of exactly the same size, and were set at exactly the same angle relative 

 to the median plane of the whole monster. 



Since this specimen was being used for the study of other systems it 

 was thought best to remove the compound eyeball as a whole and thus 

 the nerve relationships and the innervation to the separate eye muscles 

 were rendered uncertain. The determination of these latter must there- 

 fore rest upon their general shape and position and especially upon a 

 comparison with the previous specimen, in which the two inner eyeballs 



