THE HJIMOFLAGELLATES. 183 



implies, the kinetoniicleus represents that part of the nuclear 

 material which regulates the locomotor activities of the cell. 



Different ookinetes, though, at first, essentially similar in 

 nuclear constitution, exhibit considerable variation in the 

 minute structure of the cytoplasm, the quantity of reserve 

 material this contains, and the size of the body as compared 

 with that of the nucleus. In fact, the ookinetes are differen- 

 tiated into three distinct types, leadiug to the formation of 

 indifferent, male, or female Trypanosomes,with widely different 

 subsequent histories; and these cytoplasmic variations afford 

 the earliest indications of the direction of further development 

 in any given case. Schaudinn considers that this variability 

 in character stands in intimate relation with the previous 

 history of the sex-cells (gametes) which may have been, as 

 will be seen later, extremely diversified. 



(a) Ookinete of Indifferent Character and its 

 subsequent history in the Gnat. 



The cytoplasm of an indifferent ookinete (fig. 8) is fairly 

 clear and faintly staining; it usually possesses one or two 

 large vacuoles in the anterior part, but little, if any, reserve 

 material is noticeable. The pigment grains in the hinder 

 region may not all be eliminated at the first attempt, a 

 second expulsion sometimes taking place (fig. 8 e), which 

 leaves the cytoplasm free. Meanwhile, important nuclear 

 changes are occurring. The kinetonucleus becomes amoeboid 

 and gives up its material to the trophonucleus (b). The 

 result is that the eight chromatic elements of the former 

 become united, by the aid of the plastin basis, Avith those of 

 the latter, leaving the above-mentioned granule in the 

 middle. This granule divides in a dumb-bell-like manner, 

 producing a small axial spindle (fig. 8 c, a.s.), around which 

 the eight compound chromosomes arrange themselves. 

 These next split, and the halves pass to either end, forming 

 a diaster which is markedly heteropolar (c). The right 



