XIll] SEPIA 321 



which gradually closes up. Immediately over the spot where the 

 first pit closed a second pit is formed in which a second horny lens 

 is formed just over the first one, so that the lens consists of two 

 pieces, and as in the eye of the Vertebrate, there is an anterior and a 

 posterior chamber in the eye separated from one another by the lens. 



Into the anterior chamber a circular fold projects called the 

 iris, fulfilling exactly the same function as the iris of the human eye 

 or the diaphragm in a photographic camera. Outside arid around 

 the eye a circular fold acts as an eyelid. 



The cerebral, pedal and pleural ganglia are surrounded by very 

 tough connective tissue, in which the fibres, although still visible, 

 are cemented together by a material of cheesy consistence, and 

 this type of tissue is called fibre-cartilage. In this way a kind of 

 skull is formed, which sends a scoop-like extension on either side 

 over the back of the eye, covering the optic ganglia. The edges of 

 the scoop pass into ordinary connective tissue round the rest of 

 the eye. This tissue forms the wall of the eyeball. 



The otocystsare branched and embedded in the ventral wall of 

 the skull. They receive nerves from the cerebral ganglia, but as these 

 nerves traverse the pedal ganglia they appear to arise from the latter. 



The genital organ in Sepia occupies the apex of the visceral 

 hump. It is, as examination of young specimens shows, a thicken- 

 ing of the wall of the coelom, behind the pericardium. The coelomic 

 space into which the eggs and spermatozoa are shed is only shut off 

 from the pericardium by an incomplete partition, so that in Sepia 

 a state of things persists throughout life which is found only in the 

 embryos of some other forms (Fig. 146). 



The genital duct is present only on one side, the left, and is 

 produced into a prominent papilla which in the male is used as a 

 penis (Fig. 143). The outermost part of the duct in the male is 

 a wide pouch in which the spermatozoa are welded into masses and 

 enveloped in cylindrical cases called spermatophores. Just 

 inside this the duct receives the excretion of two glands termed 

 prostate glands; further inwards it narrows into a very fine tube 

 which opens internally into the coelom. Since in some cuttle-fish 

 the genital duct is paired and in Nautilus there are two pairs of 

 kidneys, while the genital ducts of that animal appear to be portions 

 of the anterior kidney ducts split off, it has been suggested that the 

 genital duct of Sepia is all that is left of a missing pair of kidneys. 

 Close examination of a male Sepia will show that the base of one 

 of the short arms is modified because it is somewhat broader than 

 the rest ,and the suckers have a tendency to be obliterated. In 



6. & M. 21 



