1883.] Physiology of Carbohydrates in the Animal System. 145 



The nature and modifications of the Crystalline Cone are next 

 described ; these afford an exceedingly difficult problem, on which 

 further work will undoubtedly throw much light, especially in rela- 

 tion to the morphology of this organ. Some details with regard to 

 the structure of the Great Rods are also added, which did not find a 

 place in the general description of the Dioptron. 



II. The Anatomy and 'Functions of the Neuron. 



The Neuron consists of three parts — the Retina, the Optic Nerve, 

 and the Optic Ganglion. The minute structure of these parts is 

 fully described in this portion of my paper. The relation of the 

 nerve fibres to the Bacilla and the Great Rods is also discussed. The 

 optic ganglion consists of parts which are clearly comparable with 

 the nuclear and molecular layers of the Vertebrate retina. 



III. The Development of the Compound Eye. 



The manner in which the Dioptron originates in the Hypoderm of 

 the insect, as well as the nature and origin of the " Imaginal Disks," 

 from which this structure is sometimes formed, is described. The 

 development of the Neuron from the nerve-centres of the head 

 presents features of extreme interest and importance, especially in 

 relation to the phenomena of Ecdysis. The segregate retina of many 

 larvee is entirely replaced at the final Ecdysis by a newly formed 

 retina, which is continuous, so that it appears as if a kind of 

 internal Ecdysis affecting the epithelial elements of the nervous 

 system occurs with the general integumental Ecdysis. 



IV. The Morphology of the Eyes of Arthropods. 



The final section of my paper is a short resume of the Morpholo- 

 gical relations of the different forms of Arthropod eye. These have 

 been already alluded to in the commencement of this Abstract. 



V. " Introductory Note on Communications to be presented on 

 the Physiology of the Carbohydrates in the Animal System." 

 By F. W. Pavy, M.D., F.R.S. Received April 5, 1883. 



My last communication (' ; Proc. Roy. Soc," vol. 32, p. 418) was 

 entitled "A new Line of Research bearing on the Physiology of 

 Sugar in the Animal System." 



During the time which has since elapsed, I have been actively 

 continuing my investigations in the direction started, and the results 

 obtained give an entirely new aspect to the whole subject of the 

 physiology of the carbohydrates in the animal system. 



VOL. XXXT. L 



