The Ciliiim. 193 



The structure of the large cilia (Fig. 7) is that shown in Fig. o, 

 PI. II*. ' It is seen that they are composed of a large number of tine 

 tibrils. In life these fibrils are wound together so that the whole 

 a])i)cars perfectly homogeneous. In animals subjected to pressure or 

 killed in 2 per cent, osniic acid the se^Darate fibrils appear. In an 

 animal that is breaking to pieces under pressure their fibrillar nature 

 is best seen. (Fig. G.) All the cilia of the Hypotrichs are made up 

 in a similar way. They are composed of several fibrils which sepa- 

 rate under pressure. (PI. II, Fig. 4.) These cilia vary greatly in 

 size and in the number of fibrils they contain. In many of them it 

 is impossible to distinguish the fibrils that formed each individual 

 after they have become separated. It is only on account of the size 

 and arrangement of the cilia that it is possible to be sure the fibrils 

 are not separate cilia. 



The bearing of these observations on the theories of ciliary struc- 

 ture is evident. If in the Hypotrichia we have a series of cilia grow- 

 ing smaller and smaller, all composed of definite fibrils which can be 

 separated, where are we to assume that this fibrillar structure ceases 

 and cilia become homogeneous fibers or tubes of fluid ? At the place 

 where we are unable to demonstrate a fibrillar structure ? This does 

 not seem reasonable, for our means of demonstrating these structures 

 are by far too gross. The simplest theory is that fibrillar structure 

 extends on down the scale, although we are unable to demonstrate it. 

 What we know of flagella makes this probable. 



Applicatiox of Methods to Other Contractile Tissues. 



Amoeba. 



The Amoeba has been used by many recent investigators, Blitschli, 

 Berthold, Quincke, Verworn, Rhumbler and others, as the starting 

 ])oint for their studies on contractile protoplasm. Unfortunately, in 

 their investigations they did not apply modern histological technique 

 to demonstrate structure in this form, hence the outcome of their 

 work in microscopical foams, colloidal fluids, etc., as an explanation 

 of amoeboid movement has resulted in widespread confusion in all 

 our theories of protoplasmic structure. 



Application of the methods and reagents which give the best j^repa- 



