488 



Brucke, Hannover, Helmholtz, Goodsir, and others, into the intimate 

 structure of the retina, he compares its structure with the structure 

 of the compound eye in insects, making the filamentary layer equi- 

 valent to what is called by Leydig the retina in insects, the rods and 

 cones in the bacillary layer to the conical bodies in the eye tubules 

 of insects, &c. And he explains the discrepancy between the rela- 

 tive position of this structure in insects and in the vertebrata, on 

 the principle suggested by Brucke and Hannover, and worked out by 

 Goodsir, that the light is reflected back from the choroid or back of 

 the eye in the vertebrate animal, so that the animal is, as it were, 

 looking backwards, and sees objects as reflected in a mirror ; while 

 in insects, he assumes that objects impinge directly on their visual 

 sensorium. 



The rest of the paper is occupied with an examination of those 

 insects which are destitute of eyes in their perfect state, with par- 

 ticulars relatinor to their habits and structure, and concludes with the 

 results of his examination of the interior structure of the integument 

 in the AnopJithalmus Bilimekii, Schm., from which it appears that 

 the interior texture of the thorax is a series of transverse elongate 

 cells, similar to the cells in plants, and which is known to be the 

 usual, if not the universal, structure of the chitonous integument in 

 insects ; the same cells are to be seen in the head ; but on the ocular 

 spaces where the eyes should have been, and which (in Anophthal- 

 mus) occupy a large portion of the head, these cells become enlarged, 

 and gradually less transverse, until, towards the middle of the ocular 

 space, some of them have assumed the hexagonal form usually seen 

 in the facets of the compound eye in insects; whence, Mr Murray 

 concluded, that this is possibly an atrophied or abortive eye, and 

 draws conclusions as to the manner of the development of the eye in 

 insects. 



Mr Murray also considers the question, whether these insects are 

 sensible of light, and if so, whether it is through this atrophied eye 

 or not ? He supposes they are, to a certain extent, sensible of light ; 

 but only in the same way as plants or zoophytes, and not through any 

 optical apparatus. 



