1921] NATURAL SCIENCES OF PHILADELPHIA. 121 



is drawn up in an angular lobe, to be affixed there to the inside of 

 the wall of the capsule, and this in a very curious way, by means of 

 a "nail," a very small bluish spot, which is never wanting. Very 

 likely this very fixation of one of these curtains to the border of 

 the cell is a result of the necessity for the cup (or anterior part of 

 the body) to remain open, for the veil, if it passed straight over to 

 join the border at the opposite side, would prevent small food- 

 particles falling into the cup.^ The flagella are perhaps more curi- 

 ous than any other element in this already somewhat para- 

 doxal being. There are two : the first one, which we might call the 

 principal flagellum, starts (or rather seems to start?) from 

 one of the borders of the cup, which we may consider as the right 

 one, and very soon bends to the left, describing thus the figure of 

 an arc, and finally terminates freely somewhat to the left of that 

 appendage wiiich we called the trunk. This flagellum nearly al- 

 ways proves perfectly quiet, like a bow stretched over the cell 

 as if for aprotection against the intrusion of any enemy. It is a 

 genuine flagellum, however, and from time to time begins vibrating, 

 but becomes quiet again after a moment. The second flagellum 

 is perhaps even more curious: upon looking attentively at the left 

 border of the cup, and more especially at the tip of the '' trunk," we find 

 there (Plate VI, fig. 16) two very small bluish granules, one behind 

 the other, and from the upper granule is seen to start a rigid, straight 

 thread, whose length nearly equals that of the body, the structure 

 of the thread, which diminishes in breadth from the base to the 

 summit, seems to be that of an axial filament covered with a thin 

 layer of hyaline plasma. This thread immediately turns some- 

 what to the left, and there remains quiet, like a tactile organ or 

 seta, from time to time, however, it is seen to move right or left, 

 like the hand of a watch, or, very rarely, to swing in a few longi- 

 tudinal undulations, but only to come quickly to rest again. Indeed 

 it hardly looks, like a flagellum, but is such in fact, only it 

 temporarily departs from its normal functions to acquire a new 

 importance. If we look very attentively at the anterior small 

 corpuscle of which we were just speaking, and not above but be- 

 hind it, we can just distinguish a very fine median line or thread, 

 which passes the posterior granule, then continues its way down 

 towards the bottom of the cup-shaped body. 



In short, Histiona campanula is in possession of two flagella, 

 but both seem to have been considerably modified in either struc- 

 ture or function.^ 



* I never could see the second of these two "curtains" affixed to the 

 capsule, and this second curtain is in fact so much smaller than the first that it 

 might be considered simply the normal border of the cup. 



* These statements about the flagella are the result of a good many observa- 

 tions, but the animalcule is exceedingly small and delicate, and more than one 

 doubt is left in my mind about some points of its structure. I have seen, for 

 instance, on two different occasions a very short flagellum beating at the floor 

 of the cup; was it a normal structure, or perhaps the basal part of the right 

 flagellum, torn off from the affixing blue grannule? 



