1915] Kof Old and Christiansen: On Giardia maris (Grassi) 37 



axostyle. and later in the metaphase (pi. 6, fig. 26) the new flagellum 

 grows out, forming a pair at the tip of each daughter axostyle. These 

 flagella are the most active ones in the set, a condition paralleled by 

 the intense activity of the non-flagellated projecting tip of the axostyle 

 in Trichomonas. We may therefore interpret the axostyle here as in 

 triehomonad flagellates (see Kofoid and Swezy, 1915 a, b) as the 

 intraeytoplasmie part of a flagellum, greatly expanded and therefore 

 staining less deeply than the intraeytoplasmie parts of the other 

 flagella in Giardia. 



The points of emergence of the two flagella of a pair are usually 

 bilaterally symmetrical, but may be shifted, probably by contraction. 



The axo.style (a.r., fig. A) is a flexible, hyaline, more or less deeply 

 .staining axial rod bearing on both the right and left corners of its 

 enlarged anterior end a large blepharoplast. It tapers distally to 0.5 

 its anterior diameter and terminates at the cytoplasmic margin in 

 posterior basal granule (post. has. gr., fig. A) from which spring the 

 two posterior flagella. The axostyle has been figured by Wenyon 

 (1907), Bohne and Prowazek (1908), Bensen (1908), Rodenwalt 

 (1911), and Prowazek and Werner (1914) as double. It is double 

 early in binary fission (pis. 5, 6, figs. 6-17) and such stages are 

 abundant in our material. They are, however, early stages in mitosis 

 and are preceded by a stage in which there is structurally a single 

 axostyle with two blepharoplasts. This is followed by a .stage with 

 two axostyles and four blepharoplasts, and it appears that it is these 

 later stages which have been utilized inadvertentl.y as typical of the 

 trophozoite. We regard the stage prior to this with one axostyle and 

 two blepharoplasts as the typical one prior to mitotic conditions. 



The cytostome (cyt., fig. A) is the ventral cup, bordered by the 

 deeply staining peristome consisting of two regions on either side, 

 an anterio-lateral arc {ant. perist.) and a posterior one (post, perist.). 

 The former are continuous anteriorly, being connected by a thinner 

 bridge across the gap above the anterior chiasma. The posterior 

 peristome is weaker, curves abruptly inwards from near the basal 

 granule of the antero-lateral flagellum with an arc convex posteriorly 

 and disappears near the axostyle without cross-connection to the 

 peristome of the opposite side. The cup is single, but its fundament- 

 ally double origin or fate is indicated in the anterior break in size of 

 the peristome and in the posterior interruption. The chromatic 

 peristome is a deeply staining, very heavy strand. We are unable to 



