NOTES ON NEMATODES OF THE GENUS PHYSALOPTEBA, WITH 

 SPECIAL EEFEBENCE TO THOSE PARASITIC IN REPTILES. 



Pabt ii. — A Review of the Fhysaloptera of Lizards. 



Bj' Vera A. Irwin-Smith, B.Sc, E.L.S., Linnean Macleay Fellow of the 

 Society in Zoology. 



[Read 29th March, 1922.] 



Seurat is the only author who has made any general study of the members 

 of this group, and his work is confined to the representatives of it in Northern 

 Africa, his two papers (1914, 1917) dealing with four species only. Descriptions 

 of the other species are scattered among isolated papers, often difficult to obtain; 

 and in most cases very unsatisfactory. The writers usually devote their attention 

 to characters which are common to all the species, and, therefore, of no specific 

 value. As Seurat points out, the reptilian Physaloptera form a very homogeneous 

 gi'oup; and he has done a useful service in giving a general account of the 

 Northern African forms. Most of the features which he describes are common 

 to the whole group. Briefly summarised, they are as follows: — 



Thick cuticle, transversely striated; a cephalic collarette; narrow lateral 

 wings, bearing a pair of post-cervical papillae; excretory pore, ventrally situated, 

 not far from these isapillae; two asymmetrical papillae further back, in the in- 

 testinal region; a strong tooth (external labial tooth) on the summit of each 

 lateral lip, several smaller teeth on its inner face, and a row of minute spines, 

 or denticles, on its lower border; a pair of lateral papillae on the buccal pad 

 external to each lip, and a median cephalic gland between them; a pair of lateral 

 caudal pores on the mid region of the tail, and a caudal gland at its tip; large 

 nerve ring surrounding the muscular oesophagus; vulva in front of middle of 

 body; uterus with two or four branches; caudal bursa on male tail, bearing four 

 pairs of external pedunculated papillae, surrounding cloaca, and about thirteen 

 internal papillae, usually sessile, of which three are pre-anal, and the rest, in 

 pairs, post-anal; spicules unequal, the right short and broad, the left long and 

 slender. 



With so much uniformity in the group, the determination of characters on 

 which to base specific distinctions is a difficult one. Seurat considers that such 

 characters are to be found only in careful measurements of the relative propor- 

 tions, and in the conformation of the internal organs. But considerable varia- 

 tions are found in the dimensions given of the same species by different writers. 



