78 University of California Publications in Zoologij [Vol.16 



present distinctive eliaracters which separate it from the flagellate 

 upon which these observations are based. These eharactere are the 

 point of origin of the flagella which as figured in H. parvus arise 

 laterally in two groups widely separated from one another, while in 

 the flagellate from amphibians they are anterior and closely connected. 

 The extranuclear chromidial bodies (parabasals?) are of a definite 

 shape and position in both forms, in H. parvus having a circular form 

 and occupying positions between the axostyles, while in our species 

 they are situated on the axostyles and nearer their posterior extremities 

 than in H. parvus. Further investigation on both flagellates may re- 

 veal greater similarities, but for the present it seems best to treat them 

 as separate species. I have, therefore, applied the name H exam it us 

 batrachorum to the flagellate described below. 



On account of its size, it may be confused with the smaller forms 

 of H. intestinalis. It is distinguished from this, however, principall.y 

 by the structure of its nucleus, which is unlike that of the other species 

 of Ilcxamitus. 



Morphology 



Hexamitus batrachorum is small, seldom exceeding 5 or 6/j, in length 

 by 3 or 4/x in width, and in general shape is ellipsoidal, rounded at both 

 ends (pi. 10, fig. 21). The three pairs of flagella at the anterior end 

 arise from two chromatic granules, the blepharoplast complex, which 

 are often massed together indistinguishably. These rest upon the 

 nuclear membranes and also give rise to the two slender axostyles 

 which pass through the center of the cytopla-sm, convex outwardly, to 

 the posterior border of the cell, giving rise there to the two posterior 

 flagella. Near the posterior ends of the axostyles two groups of chro- 

 matic granules are usually found, consisting of a common mass at the 

 periphery, and a granule on each axostyle a short distance above the 

 point of emergence. 



The two rather large circular nuclei have very di.stinct membranes, 

 which is one of the distinguishing characteristics of this species, as with 

 the exception of H. batrachorum and possibly one other the nuclear 

 membrane, if present, seems not to be distinct in Hexamitus. The 

 chromatin is arranged in a number of small granules or clumps, some- 

 times one or two situated centrally, frequently one in the center and 

 four or five lying on the nuclear membrane (pi. 10, fig. 21). The re- 

 mainder of the nucleus seems to be devoid of chromatin. The axostyles 



