A JVeiv Type of Infusorian : Arachnidiopsis paradoxa. 287 



What, uow, is the structure of the motile appendages? Accord- 

 ing to my observations they are tubes, filled with a clear and pure 

 liquid, very likely with water. Such is, at any rate, the appearance 

 on the living animal ; and the action of reagents goes to prove their 

 tubular nature. All the three individuals, after observation from 

 life, were submitted to the action of carmine mixed with glycerin, 

 and in all the effect of glycerin, if somewhat different according to 

 the greater or less concentration of the reagent, was such as to show 

 the tubular nature of the tentacles. In the first specimen one of 

 the tentacles suddenly contracted from its extremity to its base, 

 leaving in sight merely a rounded stump ; the other kept its length 

 and shape, but flattened ribbon-like, as if having suddenly sent 

 back to the body the internal liquid. In the second case (fig. 5) 

 both tentacles contracted at the same time, to leave only sack-like 

 expansions. In the third specimen both tentacles grew thin and 

 varicose at the end. 



We may cite another fact which might throw some light on the 

 intimate structure of the tubular wall. In a great number of 

 Infusoria it is often difficult to distinguish the striation of the 

 body, the appearance delineated by the ciliary lines on the cuticular 

 surface. Now, it becomes easy in nearly all cases to produce this 

 striated appearance by submitting the animalcule to a slight 

 <3urrent of dilute glycerin. This, whilst contracting the pellicle by 

 the rapid removal of its water, provokes shrinkings which follow 

 the ciliary lines, and, for a few minutes at any rate, the character- 

 istic striation very clearly appears. The tentacles of Arachnidiopsis 

 as already mentioned above, look quite smooth in life, without any 

 visible indication of longitudinal strife, such as might result, for 

 instance, of cilia fused together, nor, if these tentacles are 

 submitted to this glycerin reaction, is there any appearance of 

 pattern or lines. 



But at the same time these tubular tentacles may be, in certain 

 special cases, for a time extremely plastic, as the following observ- 

 ations will show : On one of the observed individuals, which did 

 not move from its place in spite of the vigorous beating of its 

 tentacles, one of these tentacles suddenly straightened, came to 

 rest, and its pointed extremity developed into a large lobe (fig. 4) ; 

 this lobe then began lightly to " taste," or " feel," some green alga 

 which was near, and I was beginning to think of a state of disease 

 or rapid disintegration of the animalcule, when the tentacle, leaving 

 the alga, recovered its pointed form and its normal shape, and 

 began to vibrate again, the animalcule remaining for an indefinite 

 time in good health and activity. The whole process may have 

 lasted two or three seconds. 



So much for the vibratory and at the same time locomotory 

 (as to which I could satisfy myself, but unluckily without adequate 

 observations) organs of this curious Infusorian. But now I should 



