Organisms Consisting of One Cell 243 



first he writes "That tlie above described structure functions 

 as a true skelatal (sup[)orting) structure, not only for the 

 retractile oesophagus, but also for the entire body, seems al- 

 together certain." ^^ The illustration shows something as 

 to its composition (figure 1 sK\ lam., indicating skeletal la- 

 minae). It is composed of plates or laminae, running length- 

 wise of the organ, and placed edgewise relative to the sur- 

 face of the creature. This organ is said to be the most rigid 

 and brittle of any in the animal, and is conjectured to con- 

 tain silicic acid. One docs well to note the section headings 

 of Sharp's description : "Organs of Locomotion," ^^ "Organs 

 of Food-taking," ^* "Organs of Defecation," ^^ "Organs of 

 Erection." ^^ An examination of figure 1 by the aid of let- 

 terings accompanying it, will give the reader some idea about 

 each of these sets of organs. 



One of these organ systems must be attended to more 

 specifically. It is called by Sharp the neuroviotor appara- 

 tus (labelled in the figure m.m. and circ. oes. ring). The 

 discovery of this remarkable system may well be regarded 

 as epochal in the history of knowledge of the protozoa, for 

 it seems to indicate the presence of a nervous system in 

 the higher members of this great subdivision of the animal 

 kingdom no whit less well differentiated and elaborate than 

 in some of the metazoa and that by no means the lowest of 

 them. "This apparatus," says Sharp, "consists of a cen- 

 tral motor mass or motorium, from which definite strands 

 radiate: one to the roots of the dorsal membranelles (dorsal 

 motor strand) ; one to the roots of the adoral membranelles 

 (ventral motor strand) ; one to the circumoespohageal ring 

 (circumoesophageal ring strand) : and several pass out into 

 the ectoplasm of the operculum (opercular fibers). Each of 

 these strands may send off one or more branches. In the 

 walls of the oesophagus, both nervous and contractile fibers 

 may be distinguished." ^^ 



