THE EVIDENCE OF THE ORGANS OF VISION 



79 



-ghr 



above its optic ganglion, and presented an appearance remarkably like 

 Fig. 32, which represents one of the simple eyes and optic ganglia 

 of a larva of Acilius as described by Patten ; then, with the forward 

 growth of the upper lip, 

 the right pineal eye was 

 dragged forward and its 

 nerve pulled horizon- 

 tally over the ganglion 

 habenulce. For this 

 reason the eye, nerve, 

 and ganglion are better 

 shown in a nearly hori- 

 zontal than in a trans- 

 verse section. 



The optic nerve be- 

 longing to this eye is 

 most evident and clearly 

 shown in Fig. 31, and in 

 the series of consecutive 

 sections which follow 

 upon this section ; no 

 doubt can arise as to 

 the structure in ques- 

 tion having been the 

 nerve of the eye, even 

 though, as is possible, it 

 does not contain any 

 functional nerve-fibres. 



The second, ventral 

 or left, eye, belonging 

 to the left ganglion 

 habenuhe is very dif- 

 ferent in appearance, 

 being much less evi- 

 dently an eye. Fig. 34 

 is one of the same 



pn. 



Fig. 34.— Horizontal Section through Brain of 

 Ammoccetes, to show the Left, or Ventral 

 Pineal Eye. 



, left or ventral pineal eye ; pn. u last remnant of 

 right, or dorsal pineal eye ; g.h.r., right ganglion 

 habenulce; g.h.l. lt g.h.l. 3 , parts of left ganglion 

 habenulce ; pi., fold oipia mater which separates 

 the left ganglion habenulce from the left pineal 

 eye ; /., strands of nerve-fibres connecting the 

 left eye with its ganglion, g.h.l. 3 ; V 3 , third 



ventricle; Y.aq., ventricle of aquseduct. 



series of horizontal sections as Fig. Sl,pn.i being the last remnant 

 of the right, or dorsal, eye, while pn.% shows the left, or ventral, eye 

 with its connection with the left ganglion habenulce. 



