Natural History of the Vorticellge. 207 



also in the broad streaks, which are just as undulated and 

 tortuous as the lines bounding them. This statement, however, 

 depends upon an erroneous observation ; for it is only the 

 narrow filaments that have a truly serpentine course, passing 

 right and left out of their lines and into the substance of the 

 neighbouring soft and broad streaks, sometimes narrowing 

 them to a very small space when the convexities of two con- 

 volutions approach each other, and sometimes widening them. 

 By this means the broad streaks acquire rather a repeatedly 

 sinuated, necklace-like appearance than a serpentine one. Is 

 such an extended and regular approximated tortuosity of 

 sharply contoured filaments such as we have before us in 

 Stentor at all conceivable, except with the existence of actual 

 filamentous structures ? If the clear streaks were, as Stein 

 thinks, only a part of the cuticula, and if the filaments were 

 produced only by its folding, they could hardly follow so regu- 

 larly serpentine a course without the production of folds on 

 the other parts of the surface of the body, as the cuticula also 

 covers the broad streaks. How, moreover, could the sudden 

 disappearance of the loops of the filaments (that is to say, the 

 shortening of the filaments during a sudden contraction of the 

 body), already described by Lieberklihn, be explained ? If they 

 were in reality folds of the skin, must they not then exhibit 

 more numerous and larger loops ? Besides we may even see 

 the clear narrow stripes of cuticula pass in a straight direction 

 over the subjacent undulated filament, so that there can no 

 longer be any doubt as to the presence and position of the latter. 

 A further argument against Stein's view is to be found in 

 the reticulate ramification of these filaments^ which is almost 

 always observable at the posterior extremity of the body, two 

 neighbouring filaments before attaining the posterior extremity 

 becoming united into a single one, whilst the broad body-strige 

 enclosed by them go no further, but terminate in a wedge- 

 shaped form in the angle of union. The filaments thus united 

 then often divide again in their further course, and again 

 amalgamate with other neighbouring filaments, and in this way 

 form an actual reticulate ramification. The extremities of 

 these filaments, whether reticulately united or running singly, 

 always attain the posterior extremity of the body (" sucking- 

 disk ") and attach themselves there. But the broad bands 

 neither form a network nor do they all reach the posterior 

 extremity of the body; they frequently terminate before it 

 without uniting with their neighbours, nay, often forming mere 

 wedge-shaped pieces between the clear strise. The broad 

 bands form merely the partially enveloping connective sub- 

 stance of the clear threads, and not vice versa as Stein thinks. 



