BY HARRY GILLIATT, ESQ. 385 



them, darted about with great rapidity, endeavouring to conceal 

 themselves beneath any vegetable matter on the slip, their motions 

 gradually growing slower ; then they revolved slowly two or three 

 times. A sudden contraction of the body followed, and, in a few 

 seconds, the appearance shown in Mr. Waddington's illustrations. 



The regularity of the fine transparent acicular fringe that now 

 surrounded the animalcule, or whether it was completely thrown 

 off, appeared to depend, as described by Mr. Waddington, on the 

 strength of the solution. In those cases when the appendages 

 were separated from the body it was not unusual to find a few spiral 

 shaped, although after careful comparison the majority were 

 rod-like. 



After examination of numerous specimens treated with the acid, 

 it seemed difficult to reconcile cilia of such length — in some cases 

 exceeding the width of the body — with the action apparent in the 

 ciliary movements of the living animalcule. But while observing 

 an example under oblique illumination, I was struck with the 

 appearance of fine lines across it, and was thus reminded of the 

 rod-like bodies or trichocysts so fully developed beneath the 

 cuticle of P. Aurelia. Referring to Saville Kent's " Manual of 

 the Infusoria," his remarks upon these bodies introduced a new 

 feature. I will quote as briefly as possible what Mr. Kent says: — 



"These structures — trichocysts — exist in their most characteristic 

 form, in the very cosmopolitan species, Paramoecium Aurelia, 

 taking the form of minute and exceedingly slender rod-like bodies, 

 or fibrillse * * * distributed in an even layer immediately 

 beneath the cuticle. * * * Under certain conditions, 

 including the use of artificial stimuli, such as weak acetic acid, 

 these trichocysts become suddenly elongated, and their distal ends 

 piercing the overlying cuticle stand out like fine, stiff, hair-like 

 setae beyond the cilia, around the entire circumference of the 

 animalcule, frequently becoming entirely separated from the thin 

 base of attachment." P. 80. 



Stein describes also the treatment of the trichocysts with acetic 

 acid. " Infnsionthierchen," p. 61. 



