The genus _Reighardia_ was established by Professor H. B. Ward, in 1899, for a Linguatulid of gulls and terns, first described, in 1861, by De Filippi. In 1910 Sambon included in this genus other similarly structured Linguatulids from crocodiles, monitors, and snakes. The genus _Raillietiella_ was established by Sambon in 1910 for a Linguatulid (_Raillietiella boulengeri_) of the African Puff-adders (_Bitis arietans_, _B. gabonica_). Amongst the characters of this genus is one of great structural and phylogenetic importance--viz., the position of the female sexual orifice at the anterior end of the abdomen, whilst in the other known genera it is at the posterior extremity. According to Prowazek, Sambon, and Laveran, the Ophidian Linguatulids, which live as blood-suckers in the air-passages of their hosts, are able to foster and transmit the hæmogregarines of these hosts. ACANTHOCEPHALA.--The early encysted stages of several species of Thorn-headed worms (_Acanthocephala_), belonging to the family _Echinorhynchidæ_, have been reported from snakes belonging to very different genera, such as _Boa_, _Tropidonotus_, _Zamenis_, _Drymobius_, _Xenodon_, _Dipsadomorphus_, _Oxyrhopus_, _Erythrolamprus_, _Diemenia_, _Naja_, _Elaps_, _Vipera_, _Lachesis_. Their further development probably occurs in ophiophagous birds. Thus, _Echinorhynchus oligacanthoides_, Rud., the immature stages of which occur encapsuled within the body cavity of _Lachesis lanceolatus_ and other neotropical snakes, when adult is found attached to the intestinal mucosa of _Milvus bidentatus_. NEMATODA.--The roundworms (_Nematoda_) so far described from snakes belong to the families Ascaridæ, Strongylidæ, Trichotrachelidæ, and Filariidæ. Some of the genera belonging to these families, such as _Cucullanus_, _Nematoxys_, _Oxysoma,_ are as yet represented by a single species in a single host; others, such as _Ascaris_, _Polydelphis_, _Heterakis_, _Strongylus_, _Diaphanocephalus_, _Physaloptera_, _Trichosoma_, number already several species more or less widely distributed. Eelworm infection (ascariasis) is very common in snakes, and not infrequently the infection is a heavy one; Sambon twice found over fifty specimens of _Polydelphis_ in Puff-adders (_Bitis arietans_). This investigator has shown that the snake eelworms undergo an encysted stage of development within the body cavity of their hosts before migrating into the intestinal lumen for the purpose of fertilization and oviposition. Thus, Redi was quite right in considering the immature, encysted forms found in one of the livers of his double-headed Asp as belonging to the same species of eelworm (_Ascaris cephaloptera_) as that which the snake harboured in its intestine.