1922] Kofoid-Swezy: Mitosis and Fission in Giardia enter ica 225 



union Ix'twcen tlie ecntrosonics via the blcpharoplasls forniins' the 

 anterior commissure. Bilateral symmetry in this instance is l)rought 

 about by the formation and persistent union of two structural units of 

 opposite symmetries, dextral and sinistral, whose stereometric relations 

 recall those of dextrose and laevidose, and of analogous albmninoids. 

 Giardia enterica differs in structural details, shape of body, contour 

 of the tail, points of emergence of the anterolateral flagella, shape of 

 the head of the axostyle, absence of basal granules cm the flagella, and 

 in shape of the parabasals, from species of Giardia in rodents. Rodent 

 species of Giardia are therefore not sources of human infection. 

 Experiment is needed to determine the host toleration and cross 

 innnunities of Giardia in cross infections, the effect of transfer upon 

 the morphological characters, and practicability of rodents serving as 

 temporary or persistent carriers of Giardia enterica of man.. 



Zoological Laboratory. 



University of Califorma. 



Transmitted November 14, 1921. 



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