382 University of California Publications in Zoology [Vol. 18 



karyosome. This blepharoplast is connected with the karyosome by a 

 rhizoplast. Exflagellation is accomplished by a shortening of the 

 flagella and a retreating of the blepharoplast into the karyosome. Such 

 a neuromotor apparatus consists only of a basal granule or blepharo- 

 plast from which arise two flagella, and a rhizoplast connecting the 

 blepharoplast to the nucleus. Such a condition is very primitive and 

 temporary. 



Next on the list is Prowazekia or Proivazekella, as Alexeieff (1912) 

 calls it, which in some phases resembles Naegleria in having no para- 

 basal body, but in its development a chromidial-like cloud is extruded 

 from the nucleus and forms a parabasal body connected to the 

 blepharoplast by a rhizoplast. At the time of mitosis the parabasal 

 body is depleted of its chromatin but reappears again during the 

 vegetative phase of the daughter organism. 



In Polymastix, Swezy (1916) found four flagella arising from a 

 blepharoplast which is connected to the nucleus by a rhizoplast and 

 sometimes to a parabasal body. 



In Trichomonas, as described by Kofoid and Swezy (1915). the 

 neuromotor apparatus consists of three equal anterior flagella, one 

 posteriorly directed flagellum which forms an undulating membrane 

 and one axostyle or intracellular flagellum. The parabasal body is a 

 long chromatin-like rod running along the inner edge of the undulat- 

 ing membrane. Rhizoplasts connect the blepharoplast to the nucleus 

 and parabasal body. The axostjde, which serves as the chief motor 

 organ when the animal is on a surface, contains numerous chromatin 

 granules which fluctuate in number, arrangement and size, denoting a 

 kinetic function of the neuromotor apparatus. 



Giardia, as described by Kofoid and Christiansen (1915), is a 

 binucleate organism equivalent to two trichomonad flagellates, each 

 containing one nucleus, and one blepharoplast at the end of the single 

 axostyle, three flagella and either a half or a whole axostyle, depend- 

 ing on the stage of growth of the organism. Around the mouth is a 

 heavy ring. The two blepharoplasts are connected by cross com- 

 missures and are anterior. The lateral flagella cross at a median point, 

 the anterior chiasma. The blepharoplasts are joined to the nuclei by 

 rhizoplasts and also to the parabasal body lying posterior along the 

 axostyle. 



Thus in Giardia there is a structural basis for coordinating the 

 two individuals. In reality each half of the organism has its own com- 

 plete neuromotor apparatus, but due to the crossing of the fibers at 



