258 CILIATE FIBRILLAR SYSTEMS 



ture, of holotrichs such as Paraniec'nnn; for the membranelle fibril of 

 Stentor and of Euplotes; and for most of the fibrillar systems of the other 

 ciliates, the accounts of which were more briefly reviewed. 



Also, the literature contains numerous records of fibrils, in a variety 

 of ciliates, which are structurally integrated into a so-called fibrillar 

 system. It is with such fibrillar systems that this review has been chiefly 

 concerned. 



Having established the identity of these fibrils and fibrillar systems 

 and, for many, their structural continuity or contiguity with other organ- 

 elles of the cells, especially the motor organelles, the investigators' further 

 interest has, of course, been concerned with the function or functions 

 which may be performed by such definitely related and integrated fibrillar 

 systems. 



It was previously pointed out that the interpretation of the function 

 or functions of these fibrillar systems has been based largely on the evi- 

 dences of their structural integration and their relationship to other 

 organelles. Relatively few of the interpretations have been made from 

 experimental evidence. From both kinds of evidence, it was noted that 

 at last four elementary functions have been ascribed by the many in- 

 vestigators to these various fibrils or fibrillar systems : ( 1 ) elasticity, ( 2 ) 

 mechanical support, (3) contractility, and (4) conductivity. 



Some examples of these included ( 1 ) Elasticity, the Spasnioyiem and 

 pellicle in the contractile stalk of the vorticellids (Entz, 1893), the axial 

 filament of cilia (Koltzoff, 1912); (2) Mechanical support. Stiitzgitter 

 system of Paramecium (von Gelei, 1929); fibrils generally (Jacobsen, 

 1931); (3) Contractility, myonemes of Stentor (Johnson, 1893; and 

 other authors), and of Boveria (Pickard, 1927); (4) Conductivity, 

 neuromotor system of many ciliates (Sharp, 1914; Yocom, 1918; and 

 other authors). 



A fifth function, "metabolic influence," not previously noted, has re- 

 cently been proposed by Parker (1929) for the fibrillar complex in 

 Paramecium (Rees, 1922) and in other ciliates, comparable to the func- 

 tion of fibrils in nerve cells. The neurofibrillar hypothesis for conduc- 

 tivity in nerves was regarded as untenable by Parker (1929). After an 

 extensive review of the evidences for and against this thesis, including 

 Bethe's (1897) experiment on the brain neurones in the crab Carcinus, 

 which showed that the nerve impulses did not have to traverse the fibrils 



