Professor A. Railliet, whilst examining specimens of _Polydelphis_ which had been preserved for nearly two months in a 3 per cent. solution of formalin, found that the ova within their uterine tubes had undergone development, and still contained living embryos; indeed, some of these hatched under the microscope, and moved very actively in the preserving fluid. This is in no way surprising, because even after several years of preservation in formalin solution the embryos of other species of eelworms (_Ascaris equorum_, _A. marginata_) have been found in a living condition. TREMATODA.--The Flukes (_Trematoda_) of snakes, so far described, belong to the following genera: _Agamodistomum_, _Astiotrema_, _Brachylaimus_, _Cotylotretus_, _Dicrocoelium_, _Diplodiscus_, _Distoma_, _Halipegus_, _Lecithodendrium_, _Metorchis_, _Opisthogonimus_, _Opisthorchis_, _Plagiorchis_, _Saphedera_, _Telorchis_, _Tetracotyle_, _Zeugorchis_. CESTODA.--Save a few larval forms (_Cysticercoides_, _Piestocystis_, _Sparganum_), the known tapeworms (_Cestoda_) of the Ophidia belong to the genera _Bothridium_ and _Proteocephalus_. PROTOZOA.--Numerous species of Hæmogregarines have been described from snakes. As a rule the forms seen in the peripheral blood are sporonts, the schizogonic cycle occurring in the lungs. The sporonts do not greatly alter their host cells; they are invariably doubled up within a more or less thick capsule. Some species show a marked sexual differentiation, others not. _Trypanosomes_, _Spiroechaudinniæ_, and _Plasmodidæ_ have also been described from the blood of various snakes. Within the alimentary tube have been found species of _Trichomonas_ and _Caryospora_. BACTERIA.--Acid-fast bacilli have been described in tubercular lesions found in snakes by Sibley, Gibbs and Shurley, Shattock, Hausemann, and Sambon. The so-called "canker," which so frequently develops in the oral cavity of captive snakes, is also a bacterial disease, due to a specific bacterium of thick, rod-shaped form. LIST OF PARASITES HITHERTO RECORDED FROM EUROPEAN SNAKES TROPIDONOTUS NATRIX, L. ACANTHOCEPHALA. _Echinorhynchus inæqualis_, Rudolphi. _Echinorhynchus polyacanthus_, Creplin. NEMATODA. _Strongylus auricularis_, Zeder. _Strongylus catanensis_, Rizzo. _Trichosoma mingazzini_, Rizzo. _Oxysoma brevicaudatum_, Zeder. _Nematoxys commutatus_, Rudolphi. _Ascaris cephaloptera_, Rudolphi. TREMATODA. _Opisthorchis caudatum_, Polonio. _Dicrocoelium assula_, Dujardin. _Diplodiscus conicum_, Polonio. _Tetracotyle colubri_, v. Linstow. _Distoma acervocalciferum_, Gastaldi. _Distoma allostomum_, Diesing. _Distoma nematoides_, Mühling. _Saphedera naja_, Rudolphi. _Brachylaimus signatum_, Dujardin. _Telorchis ercolanii_, Monticelli. _Lecithodendrium nigrovenosum_, Bellingham. _Plagiorchis mentulatus_, Rudolphi. CESTODA.