FLAGELLUM OF SOME EUGLENAE 293 



sible to see the flagellum at all when the creature is in full vigour 

 it is then usually being lashed about, and is bent and twisted in 

 all directions. It will be noticed that Mr. Ellis only claims to 

 have seen the disc when, for some reason, the organ to which it 

 was attached was thrown off. 



He says : " Out of all the numberless motile Euglenae which 

 were swimming about amongst their resting kindred, not one was 

 seen with a flagellum having a knob at its free extremity." 



Neither do I think any of the writers in Science Gossij) dis- 

 tinctly claim to have seen it on a healthy, active animal. But 

 when the flagellum is thrown off " bitten off," as has been 

 described or when the Euglena is killed by a careful application 

 of iodine, it is not at all infrequent, and I have seen it on speci- 

 mens from many different localities. 



It happened that since I thought of bringing the subject 

 before you I was looking over, for quite another purpose, a slide 

 of Euglenae mounted in April 1911. I there found several 

 instances of discs still attached. Some creatures, and some 

 Euglenae at all events, occasionally carry the flagellum stretched 

 out rigidly in front, with a small portion of the distal end thrown 

 into a coil or spiral form, usually rapidly moving. Now if the 

 creature were killed with the organ in that position, or for any 

 reason threw it off, it seems to me very probable that the coil 

 there might be but one turn in it would present just the 

 appearance we have had referred to as a disc or bulb, and that, 

 consisting of protoplasm, it would be very likely to adhere where 

 touching another part, and so retain its form as a circle. With 

 the use of an immersion objective and careful illumination, it has 

 seemed to me possible to make out a part of the circle as being 

 thicker or darker than the rest, owing to the thread overlapping 

 at that point. It must be remembered that we are dealing with 

 a very small and very transparent structure, not easy to demon- 

 strate correctly. Moreover, among the others, killed by iodine 

 or mounted, it is easy to find specimens with the flagellum much 

 twisted and thrown into " kinks." So that there are often small 

 circles at the sides instead of at the end of the thread, and 

 although these have just the same appearance as those at the 

 end, I do not think any one would suggest that it is likely a disc 

 or bulb would occur in such a situation, to say nothing of the 

 im probability of there being more than one, and these often on 



