THE OPALIXID CILIATE INFUSORIAXS. 



35 



of nucleus 0.012 mm. ; diameter of endospherule 0.0015 mm. ; cilia line 

 interval, anterior 0.002 mm., posterior 0.004 mm. In an individual in 

 an early stage of fission the dumb bell-shaped nuclei are 0.053 mm. 

 long and 0.009 mm, wide at the widest part. The cilia are not well 

 enough preserved to measure. JSIacrochromosomes 4. 



Fig. 12. — Protoopalina papdensis ; a, an ixdividoal of the ordinary sort, X 460 



DIAMETERS ; 6, ITS NUCLEI, X 1,000 DIAMETERS ; C, AN INDIVIDUAL ENTERING UPON FIS- 

 SION, X 460 DIAMETERS. 



This Protoopalina is similar in shape to a macrogamete mother cell 

 of P. intestinalis, resembling in this regard P. diplocarya or P. 

 acuta^ but its nuclei are very diiferent from those of the latter two 

 species. Like P. acuta^ it tapers posteriorly to a very elongated, 

 slender point, which is devoid of cilia, and is spirally grooved, ap- 

 pearing as if spirally twisted. The pear-shaped nuclei are quite far 

 apart but are connected by a slender thread. In the great majority 



