1919] Kofoid-Swrzy: Strehlomastix strix 5 



grown and possibl.v abnormal phases occasionally found. The linear 

 form of body and also of nucleus continues not only during the 

 trophozoite phase but likewise, in so far as we have seen the stages, 

 during botlj binaiy and multiple fission. During multiple fission 

 itself the organism becomes a greatly elongated thread with its nuclei 

 stretched lengthwise as a constricting thread in the axis of the body. 

 All trace of rounding up or sphericity seems thus to have been 

 banished utterly from both body and nucleus at all stages of its life 

 cycle. 



Size .\nd Shape op Body 



The body is ordinarily elongate fusiform, tapering subequally at 

 the two ends. Either or both ends (pi. 1, figs. 1, 7) may be some- 

 what bhint but the usual form of the anterior end is a slender cone 

 while the j)osterior one may have a trifle more convexity. Its length 

 is generally fi-om twelve to sixteen times its greatest diameter which 

 is found near the middle of the body. The shorter individuals 

 (pi. 1, fig. 5) may be only six times the diameter. These are evidently 

 recent sehizonts. On the other hand, giant individuals, which are 

 possibly approaching multiple fission (pi. 2, fig. 13), may be thirty 

 times their diameter in length, and the "plasmodial" stage of mul- 

 tiple fission (pi. 2, fig. 14) attains a length as much as seventy times 

 its own diameter. Measurements of two hundred individuals gave 

 a frecpiency curve with a marked left-hand skew with the mode at 40ju. 

 and the extreme range in length of from 20 to SSOft. One-half of 

 the individuals were included between 20 and 80/*. The longest indi- 

 viduals included those in which multiple fission was in progress and 

 it is probable that the others were approaching that phase. 



The contour of the body is not a smooth line, for the surface is 

 traversed by spiral ridges with furrows between, giving it the form, 

 except for its taper, of the shaft of a Norman Romanesque column. 

 These ridges are four in number, broadly convex and equidistant and 

 they wind about the body from the anterior end posteriorly from the 

 left over to the right. It is thus like a left-hand screw if the anterior 

 end is regarded as the tip. The steepness of the spiral varies with 

 the length of the organism, its contraction, and the phase of tlie life 

 cycle. In late stages of binary (pi. 2, fig. 17) and multiple fission 

 (pi. 2, fig. 14) much of the torsion is relaxed. In stages which may 

 be prior to binarj' fission (pi. 1, fig. 7; pi. 2, fig. 10) these may be 



