PLATE XXIV 



FlG. ioo. — Cyclopic trout embryo of type A (p. 40), 

 seen from left *ide and showing the large single eye 

 overarched by the mesial frontal process. 



FlG. ioi. — Transverse section of the frontal process 

 referred to above, showing the small approximated 

 olfactory pits (o), and the reduced olfactory capsular 

 cartilage (C). 



Fir.. 102. -Transverse section through the posterior 

 parts of the cerebral lobes in the same specimen, showing 

 the pineal diverticulum (Pin.), and the cerebral lobes 

 (F.B.), the latter being intimately united along their 

 inner surfaces. The central cavity of the brain (C.F.B.) 

 is not markedly dropsical, and the cerebral lobes are 

 almost normal in their transverse measurements (p. 41). 



Fin. 103.— Section through mid-brain of a cyclopic 

 trout embryo belonging to type B (p. 41), showing almost 

 complete obliteration of the mid-ventral groove which 

 should lead downwards into the infundibulum. Infundi- 

 bulum and hypophysis are absent. 



Fig. 104. — Section through back part of retina of 

 cyclopic eye (type B) described on p. 42, showing failure 

 of development on the part of optic nerve and choroidal 

 fissure. Pg. . . . hexagonal pigment layer ; Ret. . . . 

 retina ; n ... a few nerve fibres not perforating the 

 pigment layer. 



Fig. 105. — Transverse section of head of trout embryo 

 with supernumerary eye (see p. 59). 



L. 



R. 



R.O. 



N. 



C. 



Tr. 

 PL. 



S.o. 



!:■. 



I -ens of supernumerary eye. 



Retina ,, ,, 



Right noi trial eye. 



Right optic nerve receiving fibres from retina of super. 



numerary eye. 

 Central cavity of brain with two deep grooves in its floor, 



each of which leads downwards into an infundibulum 



and a hypophysis. 

 Trabeculae cranii displaced towards left. 

 t'alatoquadrate bar on left side ; the right bar is absent. 

 Supra-orbital liar. 

 Anterior corner of auditory capsular cartilage. 







Fig. 106. — Horizontal section of head of trout embryo 



with supernumerary eye (see p. 60). 

 J 

 L. Lens lielongiog to the left (aborted) twin head. 



CL'. Cerebral lobes belonging to ditto. 



3rd V. 3rd ventricle belonging to ditto. 



C. Cranial cartilages belonging to ditto. 



O. Functional left eye. 



CL. Functional cerebral lobes. 



CO, Cavity of optic lobes. 



OL. Optic lobes. 



Au. Auditory cartilage. 





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