1920] Kofoid: Xoineiiclature of Human Iiitcsfliial Flagellates 163 



groups of hosts, a given set of so-called species characters, and another 

 set in another species or group. The fact that G. muris occurs in both 

 Mm and Peromyscus, and possibly also in the rat, without noticeable 

 modification is an indication of the fixity of at least this species under 

 different conditions as to hosts. Noc (1908) states that he finds in 

 man Lamblia which exhibit the whole range in modifications described 

 by Bensen for his species. It is important to learn in how far Noc's 

 conclusions are critical, in how far the resemblances are superficial, 

 and in how far certain combinations of size, proportion, and structure 

 distinguish the species thus far described, and in how far these are 

 correlated with predominant relations to certain species as hosts. 



The determination of the correct specific name for the Giardia from 

 man is entangled not only with the problem of the specific distinctness 

 of the species of Giardia in other hosts than man, especially in rodents, 

 but also with matters of synonymy and priority under the Code of 

 Nomenclature. 



In our present opinion the morphological evidence indicates that 

 the several species normal to rodent hosts differ from that in man, and 

 that the Giardia of man should receive a separate specific designation. 

 Pantham and Porter's (19166) experimental inoculation of mice by 

 the Giardia from man does not necessarily invalidate the specific dis- 

 tinctness of the species of Giardia normally present in mice from that 

 found in man. 



The first Giardia to be described was that from man by Lambl 

 (1859) as Cercomonas intestinalis, but this specific name is pre- 

 occupied in Cercomonas by Diesing's (1850) transfer of Bodo intes- 

 tinalis Ehrbg. to Cercomonas, which this reviser treated as a sub- 

 genus of Bodo. 



Davaine (1875) described Hexamita duodenalis from the rabbit. 

 This also is a Giardia but the species in the rabbit is distinct- from 

 that in man and duodenalis is therefore not available for the species 

 from man. Grassi (1881) proposed the name Megastoma entericum 

 for the flagellates belonging to Giardia which he had found in Mus, 

 Arvicola, the cat, and man. In 1879 he had given the name Dimorphus 

 muris to the species from Mus and Arvicola and in 1881 proposed 

 M. entericum as a substitute with wider application. Since the species 

 in the mouse is distinct from that in man the name Giardia muris is 

 applicable only to the former. No data are available as to the status 

 of the form in Arvicola and infection in the cat is presumably derived 

 from that in mice. By elimination the specific name Giardia enterica 



