_Leptodera_ (_Anguillula_) _stercoralis_, Bavay.--In the summer of 1876 Dr Normand, of the French Marine, discovered this little entozoon in the fæcal discharges of soldiers who had been sent home invalided from Cochin-China. The patients in question were the victims of the so-called Cochin-China diarrhœa or dysentery. This disorder is endemic in character, and it had hitherto been regarded as consequent upon a variety of causes other than parasitic. Dr Normand’s discovery, as such, therefore takes equal rank with the analogous revelations made by Bilharz, Harley, Leuckart, Zenker, Weber, Lewis, and Bancroft, in respect of the particular helminthiases in man with which their names are severally associated (Bilharzia disease, Endemic hæmaturia, Cestode tuberculosis, Olulaniasis, Inter-tropical anæmia, Trichinosis, Lymphoid affections, Helminthoma, and so forth), and also, if I may be permitted to say so, with my own determinations in respect of a variety of endemics affecting animals (cestode and nematode epizoöty in the horse, the so-called grouse-disease, the pigeon-endemic due to lumbricoids, &c.). The _Leptodera stercoralis_ is a minute, smooth-bodied, simple, rhabditiform nematode, measuring when full grown 1/25″ in length, with an average breadth of 1/625 of an inch. The embryos at the time of their extrusion measure only 1/250″ in length, but by the time at which a rudimentary vesicle representing the uterus begins to form, the females have already attained a length of about 1/83″. The males and females are of nearly equal size. The transition from the embryonal state to the higher larval conditions is accompanied by a change of skin, after which the digestive and reproductive organs are gradually but rapidly formed and completed. These changes have been minutely traced and recorded by Professor Bavay, who also compares the entozoon with the genera Rhabditis and Leptodera, in either of which genera the worm might be placed. I have accordingly adopted the nomenclature suggested by Bavay. [Illustration: FIG. 48.--_Leptodera intestinalis._ _a_, Adult female, and separate figure showing a portion of the body with the ova _in sitû_. The two outlined figures represent profile and front views of the tail, respectively. _b_, _c_, Eggs with imperfectly formed embryos. _d_, Larva. Highly magnified. After Bavay.]