Having observed very singular phenomena in the crystalline lenses of fishes and quadrupeds when exposed to polarized light, I was led to examine their anatomical structure, with the view of ascertaining if it had any relation to these optical appearances. Leeuwenhoek and Sattig had previously made some progress in this research, but their methods of observation were ill fitted for so delicate an inquiry, and experience soon convinced me that the structure of the lens could not be thoroughly investigated either by the microscope or the scalpel. Anatomists had long regarded the crystalline lens as composed of concentric laminae, and these laminae of minute fibres; but M. Soemmerring, in his work on the Human Eye, published in 1804, regards this structure as the effect merely of maceration in alcohol, and maintains that it does not exist in the recent or the living eye. This decision, which its author has supported by many plausible but unphilosophical and inefficient arguments, appeared to set aside all the results which had been obtained by preceding inquirers, and rendered it necessary for me to adopt a new mode of investigation, which should not be liable to the same criticism.