"FlGSt 43-46- Horizontal sections of double monster (union at optic lobes), belonging to the same type as the specimen 

 illustrated in PI. I. figs. 4, 5, Pis. VIII., IX. figs. 35-38, and Pis. X., XI. figs. 39-42. The moulding of the adjacent eyes and brain 

 parts presents, however, some important differences when compared with the two last-named sets of figures. The eyes are turned 

 towards one another, so that the common lens lies buried below the surface in the centre of the globe. ' The optic lobes show 

 greater evidence of duplicity, as also do the parts round the iter and the fourth ventricle. Owing to curvature of the specimen, 

 the body is cut through obliquely, as in Pis. X., XI. figs. 39-41, and shows a double condition of the notochord and of certain 

 other structures. The gullet and rest of the alimentary canal are single, but there are two swim-bladders and air-ducts. For 

 general references see under PI. I. fig. 4. 



FIG. 43. Horizontal section of the embryo described above, 

 passing through upper parts of eyes, brain and auditory organs. 

 The fused adjacent sides of the optic lobes form a rounded 

 mass, projecting into the central cavity. Dorsally, the sagittal 

 planes of the twin fore-brains are much inclined towards one 

 another. ( x 14.) 



FIG. 44. Horizontal section of the embryo described above, 

 passing through the middle of the outer eyes and of the 

 auditory organs. The mesial optic lobe mass, referred to 

 under Fig. 43, is now larger. The mesial muscular mass 

 between the two notochords is also to be noted. ( x 14.) 





FIG. 45. Horizontal section of the embryo described above, 

 at a deeper level than in the last two figures. The adjacent 

 olfactory pits and the two adjacent eyes with single lens in the 

 middle of the globe are seen, as also are the two sets of in- 

 fundibular outgrowths and the origins of the two swim- 

 bladders. (xi4.) 



FlG. 46. Horizontal section of the embryo described above, 

 at a deeper level than in Fig. 45. The globe made up of the 

 fused adjacent eyes is cut in median section, while the outer 

 eyes show their choroidal fissure and places of entrance of the 

 optic nerves, (x 14.) 



PL. XII. 



