162 MR. NEWPORT ON THE OCELLI 



" a minute tegumentary follicle coated by dark pigment, which receives the end of a 

 special cerebral nerve," and he exemplifies this by reference to the eye of the Myxine and 

 Lancelet, and also to that of the Amblyopsis spel&us*, a fish which constantly resides in the 

 dark caverns of Kentucky, and which at first was supposed to be completely eyeless, but 

 which now is shown by Tellkampf t to possess eyes ; — the fish, Amblyopsis, like the insect, 

 Anthophorabia, having been misobserved in this respect, through imperfect investigation. 

 The condition of the eye in these low forms of the organ in Fishes is very similar to that 

 of the simple eyes in their lowest form in Insects. The eye of the insect, as long ago 

 shown in my paper on Meloe, read to this Society, is, like all the external organs of its 

 body, a tegumentary structure. It originates in a little cavity, pit, or simple depression, 

 in the substance of the tegumentary portion of the head, which, lined with pigmentary 

 substance, is more or less deep in proportion to the perfection of the organ, and it is 

 covered in on its exterior by a transparent portion of the external layer of tegument, which 

 forms the cornea, and affords a free passage to light, which is received by the retina, or 

 termination of a cerebral nerve at the base of the organ. This is the principle of construc- 

 tion, and the condition of the ocellus, or simple eye in Anthophorabia (Tab. X. fig. 10 b, c), 

 as in other insects. In the most perfect form of ocellus in Insects, an iris and a lens also 

 are present. The ocelli of the vertex, in Anthophorabia, are the most perfect in their 

 structure (c). The cornea is quite transparent, nearly circular in shape, and well-defined 

 at its margins, as may be seen, with some care of manipulation, with the microscope ; 

 but it is much flattened, and forms only a very slight portion of a segment of a sphere. 

 The choroid is deeply coloured, being formed of distinct pigmentary granules, which clothe 

 the shallow cup-shaped cavity of the organ. The presence of this pigmentary choroid 

 indicates the light-receiving function of the organ, but whether this organ be simply 

 capable of appreciating light, or whether also of distinguishing form, its focal length of 

 vision must necessarily be very short, so that in this respect the facts of structure accord 

 well with the observed and with the presumed habits of the insect. 



The ocelli at the sides of the head (b) have the same general structure as those on the 

 vertex, but are much more imperfect, in so far as respects the choroid ; so that these ocelli 

 may fairly be regarded as simple appreciators of light. The form of the cornea in these 

 is an elongated oval, or lozenge- shape. 



In all well-ascertained conditions of the simple eye in insects, the organ is found to con- 

 tain, in addition to the parts mentioned, a concentrating refracting medium, a lens-like 

 body, which is situated immediately behind the cornea, as was shown by Muller in the 

 Arachnidaf. This lens-like body does, I believe, exist in the female Anthophorabia ; but 

 whether this structure, on which chiefly distinct vision and the power of the single eye of 



* Loc. eit. 



t M. Th. G. Tellkampf in Miiller's Archives for 1844, p. 381. See also fig. 50, p. 176, Owen's Lectures, 1846. 

 Also the remark in Dr. F. H. Troschel's Report on Ichthyology for 1844, that the Amblyopsis spelceus " possesses mi- 

 nute eyes covered by the integument" (Ray Society, Reports on Zoology, 1847, p. 563). This is exactly what might 

 be expected, seeing that, in all animals, the cornea is, originally, continuous with and forms part of the tegument. 



X Physiol, des Gesichts-sinnes, p. 315. Annales des Sciences Naturelles, t. xvii. p. 232. Meckel's Archiv, 1829, 

 pp. 38, 208. 





