DERIVED ORGANIZATION 127 



Myophrisks of the Radiolaria are contractile strands which are 

 fastened by their distal ends to the extremities of the axial bars of 

 the Acantharia. The proximal ends fray out into fibrils which are 

 lost in the reticulum of the gelatinous mantle or calymma, of the 

 ectoplasm. By their contractions the calymma is drawn up to the 

 ends of the axial bars whereby the diameter of the organisms is 

 increased and its specific gravity decreased, the reverse occurring 

 with their relaxation. The myonemes thus seem to play a part in 

 the hydrostatic activities of these Radiolaria, although this func- 

 tion is difficult to understand, since the change in specific gravity 

 is usually interpreted as a means by which these motionless forms 

 escape from adverse conditions on the surface. We should expect, 

 however, that rough water or other surface conditions detrimental 

 to the organisms, would be sources of stimulation which should 

 cause the contractile elements to contract and thus to defeat their 

 apparent purpose by decreasing the specific gravity. 



Coordinating Fibers. — If a single cilium of a resting Pleuronema 

 be touched the entire organism responds. Here and in similar cases 

 there appears to be a definite tactile function. In flagellates also 

 it is not improbable that certain flagella, as the anterior flagella of 

 Caduceia theobromae described by Franca (1918), or indeed possibly 

 all flagella have a more or less well-developed sensory function. 

 In ciliates, such as Paramecium caudatum, with a uniform coating 

 of cilia, the motile elements do not all beat simultaneously, but a 

 wave of contraction, beginning at the anterior end, passes down the 

 cell to the posterior end. Cilia in the same transverse row beat 

 synchronously, but each cilium in a longitudinal row begins its 

 beat shortly after the cilium anterior to it has started and before it 

 has ended its beat (Verworn). The cilia of transverse rows are thus 

 synchronous, those of longitudinal rows metachronous in their con- 

 tractions, a phenomenon which accounts for the wave-like movement 

 of undulating membranes which are formed of fused cilia of longi- 

 tudinal rows (well shown in the undulating membranes of the 

 Pleuronemidae). According to Alverdes (1922) isolated cilia with 

 basal body may act independently of a coordinating system but 

 they do not react to stimuli. 



This regularity of cilia movement which may be easily seen in 

 the uniform ciliary coating of Nyctotherus ovalis from the cockroach, 

 indicates the transmission of impulses and the activity of some coor- 

 dinating mechanism in the cell which today we attribute to the 

 silver line system. Entz, Maier, Schuberg and many other observers 

 have found distinct fibers connecting the basal bodies of protozoon 

 cilia and have generally interpreted them as myonemes. Since 

 forms like Nyctotherus, Frontonia, Paramedium, etc., which do not 

 contract, show the same rhythmical action of the cilia, it is prob- 

 able that the threads connecting their basal bodies are not myo- 



