1914] Sharp: Diplodinium ecaudatum 83 



Here again attention is called to the fact that the literature on these 

 animals is devoid of any suggestion of the structure which is here 

 described. The possibility of this structure functioning as a motor 

 apparatus or even possibly as a neuromotor apparatus is suggested and 

 for purposes of description the designation neuromotor apparatus will 

 be used, and its constituent parts will be described as a motorium or 

 motor mass (m. m., figs. B, C; pi. 4, fig. 3; pi. 6, figs. 14-16; pi. 7, 

 figs. 21-24, 33), a dorsal motor strand (d. m. sir.), a ventral motor 

 strand {v. m. str.), opercular fibers {op. /.), an adoral lip strand {ador. 

 Up str.), oesophageal fibers (oes. /.), and a circumoesophageal ring 

 {cir. oes. ring). The term motorium, as applied here, is used in its 

 anatomical or neurological sense, i.e., the common center of motor 

 influences. It may be, however, that we have here a condition in which 

 nervous, contractile, and supporting elements are in so primitive a 

 stage of evolution as to be incapable of separation into purely nervous, 

 purely contractile, or purely supporting structures. The structural 

 conditions and the observations on the living animal in activity, how- 

 ever, suggest emphasis upon the neural rather than upon the con- 

 tractile, or supporting nature of these structures, though not excluding 

 the latter two. They are probably comparable to the simple fibres of 

 Stent or figured by Neresheimer (1903) and regarded by him as 

 " neurophanes. " 



Motorium. — The motorium or motor mass (m. m., figs. B, C ; pi. 4, 

 fig. 3; pi. 6, figs. 14—16; pi. 7, fig. 33), is a very small mass of chem- 

 ically differentiated tissue located rather deeply in the ectoplasm, just 

 above the base of the left skeletal area (l. sk. a., figs. B, C ; pi. 4, fig. 3) 

 and between the left extremities of the dorsal and adoral membranelle 

 zones. This motor mass was first noted in sections stained with my 

 modification of Mallory's connective tissue stain. It was discovered 

 that here, in the region just described, was a mass of tissue which had 

 stained rather intensely and showed by transmitted light the same 

 bright red color which was noted in the case of the micronucleus. 

 Further investigation along this line revealed the fact that not only 

 was this mass constant but (1) that it was connected dorsally, by 

 means of a delicate strand, i.e., dorsal motor strand {d. m. str., figs. 

 B, C; pi. 4, fig. 4), with the bases of the dorsal membranelles, also 

 a branch strand ran along the base of the inner dorsal lip, i.e., the 

 dorsal lip strand {d. lip str.) ; (2) that a fine strand, the ventral motor 

 strand {v. m. str.), ran from it to the bases of the adoral membranelles, 

 also that a branch strand left this ventral motor strand and passed 



