(386 William Patten 



(muscular?; band. The retina is nearly hemisplierical, and contains a 

 deep row of large nuclei and a superficial layer of more numerous, smaller 

 ones. Accordingto Sars' description, this layer should contain bright red 

 pìgment, although in the preparations I examined the cella were color- 

 less, the pigment haviug beeu extracted by the reagents. The cavity 

 of the optic cup is almost completely filled with a mass of rods (Sars' 

 »flabelliform bündle of fibresif), which are remarkable on account of the 

 long , vertical , median rods , and the shorter, horizontal ones, on the 

 side walls of the cup. Beneath the retina is an extraordinarily thick, 

 (laminated) layer, or argentea, nearly hemispherical, and remarkable 

 on account of the uniformity in the thickness of its peripheral and 

 centrai parts. The great development of the lateral rods, and of the 

 peripheral part of the argentea is a correlated and dependent condition, 

 probably due to the great amount of lateral light reflected by the peri- 

 pheral parts of the argentea upou the lateral rods. The vertical rods pro- 

 bably receive the direct vertical rays from the lens, and the same a second 

 time after their reflection by the underlying argentea. The general 

 tendency has been to regard these remarkable organs as eyes, on 

 account of their evident similarity to them, though Sars has come to the 

 conclusion that they are not eyes, but luminous organs. But let us con- 

 sider wliat a luminous organ is, and how it originated. It certainly must 

 be of some decided advantage to the animai, else it could never bave 

 originated. It is extremely improbable, if not impossible, to suppose 

 that such highly complicated organs could bave been developed by a 

 series of graduai chauges, for the purpose of frightening other animals. 

 Besides luminosity is too common to suppose that it would aifect auy 

 nocturnal animals — the only ones to be frightened by it. They 

 could not serve as sexual attraction , since they are present in both 

 males and females. It is extremely improbable that they could bave 

 originated as luminous organs, tobe used as a help in capturing 

 prey. It is only possible to suppose that their luminosity w^as a newly 

 acquired property, origiually, only a secondary, oriucidentalone. 

 For instauce, it would be very easy for au eye, with a well developed 

 tapetum and lens, to be transformed into a luminous organ, provided 

 the rods, or some other substance in the optic vesicle, as the vitreous 

 body, should acquire highly phosphoresceut properties ; the lens and 

 concave argentea would then act like a miniature dark-lantern, in 

 which the phos])horescent substance is the light, the argentea, a con- 

 cave reflector of the most perfect description, and the optic lens, 

 the bulFs eye lens of the lantern. If such a transformation took place, 



