164 THE PINEAL ORGAN 



On the dorsal aspect of the cranial cartilage of Sepia, overlying and 

 protecting the cerebral ganglia is another endoskeletal structure, namely 

 the nuchal cartilage. The hypothetical significance of the existence 

 of these skeletal elements in invertebrates will be discussed later in 

 connection with Gaskell's comparison of the entosternite of Limulus 

 with the cartilaginous skeleton of Ammocoetes. 



The Eyes of Sepia 



The conspicuous large eyes of the cuttlefish have attracted the 

 attention of many zoologists, among the more recent of whom may be 

 mentioned Faussek (1900) and Koeppern (1909). They are much more 

 highly organized than those of Nautilus and Triton and have a superficial 

 resemblance to the lateral eyes of vertebrates, since they have a lens with a 



Rh. 



7 R.+GC. N.G 

 P.L. 



Sec Co 

 A.Ch 



JgiPl^Cil.B. & S.L 

 N O.E.S. ^PCh&V 



Op.L. 



Fig. 121. — Transverse Section through the Head of an Octopus (Sepiolia) 



(original). 



A.Ch. : anterior chamber. 

 A.S.L. : anterior segment of lens. 

 C.Ep. : cutaneous epithelium. 

 Cil. B. & S.L. : ciliary body and sus- 

 pensory ligament. 

 F. : cavity of funnel. 

 Inf. C. : infundibular cartilage. 

 Ir. : iris. 



M.C.L. : middle cerebral lobe. 

 N.G. : nerve ganglion. 

 O.C.F. : outer cutaneous fold of eye. 



OES. : oesophagus. 



Op. L. : optic lobe. 



P. : pupil. 



P. Ch.& V. : posterior chamber and 



vitreous body. 

 P.L. : pigment layer of retina. 

 Pr. Co. : primary cornea. 

 P. S.L. : posterior segment of lens. 

 R+GC. : retinal and ganglion cells. 

 Rh. : rods. 

 Sec. Co. : secondary cornea. 



The names which are employed to denote the various parts of the invertebrate 

 eye must not be regarded as implying a morphological correspondence with 

 similarly named parts of vertebrate eyes. (R. J. G.) 



