UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



ZOOLOGY 



Vol. 16. No. 3. pp. 30-54, pis. 5-8, 1 figure in text November 19, 1915 



ON BINAEY AND MULTIPLE FISSION IN 

 GIARDIA MURIS (ORASSI) 



BY 



CHARLES ATWOOD KOFOID axd ELIZABETH BOHN CHRISTL\NSEN 



lu the last edition of Kolle and Wassermann 's HandbKcIi der 

 Pathogenen Mikroorganismen, Jollos (1913) states that division stages 

 of Lamblia (= Giardia Kun.stler) have never been observed among 

 the great numbers of individuals found as parasites in the intestinal 

 lumen of mammals, ".so dass eine Vermehrung auf diesem Stadium 

 kaum anzunehmen ist." He easts doubts upon Noe's (1909) reported 

 binary and multiple fission as not well grounded, but cites the oft- 

 observed multiplication in cysts as insufficient to explain the enormous 

 numbers of the parasites. Alexeieflf (1914) and Schaudinn (1903) 

 described as copulation cysts those containing two individuals, a view 

 to which Wenyon (1907) adheres, though Bohne and Prowazek (1908) 

 distingiiish certain cysts as multiplication cysts and others as copula- 

 tion cysts, and Kodenwaldt (1911) is skeptical as to the reliability of 

 these earlier interpretations, especially as to copulation and autogamy, 

 as was also Dobell (1909) before him, on other material, however. 

 'Alexeieff (1914) explicitly states "pas de division a I'etat libre," and 

 Prowazek and Werner (1914) in their very recent summary of the 

 literature and their reinvestigation of the structure and development 

 of Lamblia state emphatically that multiplication by binary, and 

 occasionally multiple fission occurs only in the cysts, though they 

 find one case of spindle formation in the free stage. 



This question as to the limitation of reproduction to the encysted 

 stage is of more than technical interest, since it might appear, if true, 

 to limit the extent of infection to the number of ingested spores. In 



