• 1The occurrence of the combined anomaly of ‘hare-lip’ and cleft palate in embryos of three species of snakes is recorded.
  • 2Study of serial sections of these embryos shows that the cleft, which is unilateral in three cases and bilateral in one, extends from the nostril to the choanal opening. It passes between the premaxilla and vomer medially and the maxilla and palatine laterally. The shape of these bones, and of the cartilaginous nasal capsule, is not grossly abnormal, but the cleft passes through the septomaxilla dividing it into two portions.
  • 3The organ of Jacobson related to the anomalous cleft is slightly abnormal in shape but has developed a complete duct which opens on to the palate in the usual situation. The lachrymal duct, instead of opening into the duct of the organ of Jacobson, ends blindly on the outer side of the nose.
  • 4A comparison is made with the condition in mouse embryos with cleft palate, and the mode of formation of the palate, as well as the morphogenesis of anomalous cleft palate in Squamata and mammals is discussed.