384 University of California Publications in Zoology [Vol. 18 



flagella, axostyle and undulating membrane in such forms as each or 

 all of these structures may be found. With this idea of the character 

 of the blepharoplast, it is easy to see how the motorium is similar to 

 it for the motorium, too, is a structure to which part of the motor 

 organs are connected. In this case we must consider the basal granules 

 of the cilia, cirri, and membranelles as being secondary rather than 

 primary structures. This is interesting in that structures may, in the 

 process of evolution, develop from the fibrillar system in some such 

 manner as the development of the ciliary apparatus of the spermato- 

 zoids of some plants, where a fiber grows out from the blepharoplast 

 and becomes the band which breaking up forms the granules to which 

 the cilia are attached (Webber, 1897; Ikeno, 1898). Such a concep- 

 tion does not permit of comparing the basal granules found in eiliates 

 to the blepharoplast but makes them of secondary importance, leaving 

 the similarity existing between the motorium and blepharoplast. 



A second point of similarity upon which an homology may be based 

 is the connection between the neuromotor apparatus and nucleus. In 

 flagellates such a connection is very evident and consists of a rhizoplast 

 joining the nucleus to the blepharoplast. In eiliates this connection 

 has not been definitely established, but in his description of Diplo- 

 diniuni ecaudatum Sharp (1913) shows that certain fibers connecting 

 with the neuromotor apparatus extend out into the cytoplasm and end 

 in the vicinity of the micronucleus. Thon (1904) also described a 

 system of fibers in Didinium nasutum which extended from the region 

 of the esophagus to a point near the nucleus. In Euplotes patella 

 there is no indication that a connection exists between the nucleus and 

 neuromotor organs, but since other parts of the neuromotor apparatus 

 so closely resemble the neuromotor apparatus of Diplodimum we may 

 assume that in the evolution of Euplotes the connection between the 

 neuromotor apparatus and nucleus has dropped out, and that this 

 coordinating mechanism at the time of binary fission develops inde- 

 pendently of the nuclear phenomena. However, such an idea cannot 

 be completely verified until we know the entire life cycle of Euplotes 

 and the development of its neuromotor apparatus at the time of 

 sexual reproduction. 



In the above discussion an attempt has been made to show that 

 even in forms as diverse in structure as eiliates and flagellates there 

 exist structures which are probably homologous. The motorium and 

 blepharoplast may be considered homologous structures, both being 

 centers around which the motor organs are developed in such a way 



