208 The -Eye of the Cod-fish. 



although it must be confessed that the filament in question bears 

 a very considerable resemblance to the radial filaments attached 

 to the similar twin-cones of the perch as represented by Kolliker 

 and H. Muller in Ecker and R. Wagner's beautiful Icones Phy- 

 siologicce, plate 19, fig. 13. In support of my opinion, how- 

 ever, that the protruded filaments I have described are neither 

 more nor less than the so-called baccillary prolongations (Zap- 

 fenstabchen) from the outer, choroidal, or lower ends of the 

 cones, I may observe that even in the human retina the true 

 baccilli of the cones have been seen expanded at their free ends, 

 whilst the radial filaments in the perch do not immediately 

 proceed from the cones, but are connected thereto by the inter- 

 calation of nucleated corpuscles (Zapfenkomer) placed at the 

 upper pole of the cones. Whatever interpretation be eventually 

 put upon the phenomena I have here recorded, those members 

 of the Brighton Microscopical Society who were present on the 

 occasion to which I have referred, will bear me out as to the 

 occurrence of many of the changes above described, and I con- 

 sider myself particularly fortunate in having been assisted in 

 the determination of these facts by Dr. William Addison, E.R.S., 

 F.L.S., Mr. J. Jardine Murray, F.E.C.S.E., Dr. Hallifax, Mr. 

 D'Alquin, and especially also by Mr. Hennah, whose skilful 

 manipulatious are so well known to microscopists. Let me add, 

 in conclusion, that after a due consideration of the foregoing 

 particulars, associated with many data previously known to 

 science, as well as other personal experiences not here recorded, 

 I think the following deductions maybe legitimately drawn and 

 placed on record. 



1. That the occurrence of opaque, white, stellate, circular 

 patches in the sclerotic of the cod is almost invariable in old 

 and tolerably full-grown examples of this fish, and that their 

 contents resemble the so-called pseudo-naviculee of G-rcgarince. 

 They are, in point of fact, tailless Psorosioermice, and therefore, 

 also perhaps, non-ciliated zoospoores, whose genetic relations 

 with Oregarince are not clearly made out. In my opinion the 

 Psorospermice are referable to the lowest forms of vegetable life, 

 and should be transferred from the Protozoa to the Chlorospores, 

 or Confervoids ; or, to speak more precisely, they should come 

 somewhere between the Palmellacece and Desmidiaccce. 



2. The so-called choroid gland of the cod and other osseous 

 fishes, is neither glandular, muscular, nor erectile, but is a spe- 

 cialized vascular plexus of capillaries. It is in no way con- 

 nected with the adaptation of the humours of the eye to 

 varying focal distances, but is probably intended to modify tho 

 circulation of the blood in a situation where, from the proximity 

 of the heart, a strong impulse would interfere with the reflec- 

 tion of a correct image from the choroid. In cartilaginous 



