292 J. BURTON ON THE DISC-LIKE TERMINATION OF THE 



PI. xx. fig. 29 ? " Saville-Kent says, in the paragraph referred to : 

 " An interesting local variety of E. viridis has been recently 

 described by Mr. M. H. Robson, of Newcastle-upon-Tyne, in 

 which the distal extremity of the flagellum presents an inflated 

 knob-like aspect, as shown at PI. xx. fig. 29. Possibly such 

 modification of this important organ represents a phase pre- 

 liminary to its entire withdrawal, and antecedent to the 

 entrance of the animalcule upon the encj 7 sted or resting stage." 



In Science Gossip (1879) there are several letters about the 

 phenomenon, one on p. 231 by Mr. Robson, with the original 

 drawing from which Saville- Kent's figure is taken, and also two 

 other forms of Euglenae with identical organs. Referring to 

 them, Mr. Robson says: "These may be of interest, as I, at all 

 events, have not met an observer who has previously noted this- 

 peculiarity." In a letter on p. 136 another writer mentions a 

 case where in a large number of Euglenae " the flagellum was in 

 each case bulbed." And he draws the singular conclusion that 

 these were not true Euglenae, but suggests they may have been 

 a larval form of the rotifer Hydatina senta. In a letter, p. 159,. 

 Mr. Robson writes of E. viridis and its " sucker bulb," and of the 

 existence of " the bulb siphon, sucker, or whatever it is." On 

 p. 256 there is a letter from Mr. George headed, " E. viridis and 

 its bulbed flagellum," and he makes reference to the fact that 

 " on one occasion, whilst closely watching the contortive move- 

 ments of a full-grown specimen, I was much surprised to see the 

 little animal ' bite off",' if I may so term it, the flagellum, which 

 immediately floated away." It is clear at least from all this that 

 observers a good many years ago saw the structure, and that it 

 created a good deal of interest and some speculation as to the true 

 interpretation of the appearance. 



Now, to return to Mr. Ellis's question, " What is the little 

 disc " attached to the distal end of the flagellum of some 

 Euglenae ? After some considerable attention to the subject,, 

 and observation of many examples, I have come to the conclusion 

 that there is no disc, no bulb or sucker, or anything of the kind 

 at the end of the flagellum. The appearance which has given 

 rise to the idea can be correctly accounted for in another 

 manner. I have often seen the disc since Mr. Ellis first called 

 attention to it, but do not remember ever seeing it on a flagellum 

 in active use by a healthy Euglena ; in fact, it is almost impos- 



