Zbb BULLETIX IL'U, UNITED .STATES NATIONAL MUSEUM. 



major grooves extending through the length of the body, and sec- 

 ondary striae (probably faint grooves) interpolated between these. 

 The secondary striae are more evident anteriorly, but I have seen 

 them also throughout the body. In numerous species of Opalinids. 

 the primary grooves bear rows of cilia throughout the length of 

 the body, and in addition there are interpolated anteriorly shorter 

 grooves also bearing rows of cilia. These grooves are not the same 

 as the pellicular striae, though they may perhaps arise by more 

 emphatic development of some of the latter. This all recalls vividly 

 the pellicular sculpturing of some of the less modified Euciliates 

 and the manner of insertion of their cilia. The pellicular sculptur- 

 ing is much more developed in most Euciliates (see Maier, 1903). 

 The Opalinidae, therefore, in the character of the pellicle, diverge 

 from the Plasmodroma and markedly resemble the Euciliata. We 

 should, however, note one group commonly classed among the Flagel- 

 lata, which has some representatives which are somewhat Opalinid- 

 like in the character of their pellicle and the insertion of their cilia. 

 The genus Trichonympha has a pellicle with numerous spiral ridges 

 bearing rows of cilia. To this comparison a return will be made later. 



The division of the cytoplasm into ectosarc and endosarc js gen- 

 eral among Plasmodroma and Euciliata and shows nothing dis- 

 tinctive. The inclusions in the ectosarc and endosarc, which in the 

 Opalinidae we have called spherules, and the more diifuse aggre- 

 gations of paraglycogen ( ?), can hardly be compared with structures 

 in the Plasmodroma and Euciliata, for our knowledge of the mor- 

 phology, physiology and origin of these structures is very inadequate 

 throughout the Protozoa. 



The excretory organ in the Opalinidae is very lowly in its develop- 

 ment, consisting of a posterior pore, usually closed but reopening 

 in the same spot, connected with a more or less well-developed 

 vacuole or series of vacuoles along the main axis of the body. The 

 excretory vacuole in some species, especially the flattened ones, may 

 be restricted to the posterior end of the body or may be whoU}^ ab- 

 sent. When well developed it runs as a series of more or less con- 

 fluent vacuoles along the axis of the body, often almost to its an- 

 terior end. It is in close proximity to the nuclei as it passes them, 

 and may be branched in the region of the posterior nucleus. This 

 is a simpler, less definitely formed excretory organ than is found 

 among Euciliates. It is little more than a more or less transient 

 fusion of enlarged alveoles, forming a tube often considerably in- 

 terrupted and with very irregular outlines. Yet this lowly de- 

 veloped elongated organ suggests comparison with the much more 

 definite excretor}- tubule, say, in HopUtophrija (Metcalf, 1909) and 

 Pycnothrix (Schubotz, 1908), In spite of its vagueness it is of the 

 general type familiar in elongated Euciliata. Its contractions are 

 not definite and regular, but occur occasionally at irregular intervals. 



