THE LIFE HISTORY OF A NEW MONAD. 



Bv AUBREY H. DREW. 



W'ltli illKsticitioiis from camera lacula ilriiicnina by the Writer. 



In December, 1908, whilst examining microscopicalh' 

 a sample of water from a pond at Keston, Kent, I 

 first observed the organism of which the life-histor\- is 

 here given. \\'hilst swimming, this form seemed to be 

 possessed of but one flagellum. which wasapparentK" 

 motionless. At first its method of locomotion seemed 

 obscure, but by accurate examination with high powers 

 it was seen to possess a second flagellum \er\- much 



The central part of the body is generally verv 

 granular. When stained the organism is seen to 

 possess a nucleus, which is usuallv situated towards 

 the side of the body. In swimming, the smaller 

 flagellum is in constant motion to and fro. the lash- 

 like extremity of the long flagellum being also usuallv 

 in vibration. The long flagellum appears to be of use 

 also for steering purposes, but its main utilit\' is 



FiGCRE 1. 



Normal f r e e 

 swimming form. 



FiGCKE 2. Fk.lre i. 



The organism during feeding. 



FiGLRi; 4. Figure 5. 



The ingestion of other Monads. 



smaller than the other and curved round towards the 

 bodw This second flagellum was in rapid motion 

 during swimming. \'ery careful and repeated obser- 

 vation revealed the fact that the other flagellum was 

 also used in swimming, as it had a fine whiplash- 

 like extremitx'. which was in rapid motion. I deter- 

 mined to work out. if i)OSsible, the life-histi>r\- of the 



The 



undoubtedh' in feeding, as will be seen later, 

 normal form, after swimming for a period which ma\- 

 var\- from minutes to hours, becomes amoeboid and 

 finally ceases movement. A more or less globular 

 shape is now taken on, and the whole of the long 

 flagellum is vibrated with a serpentine kind of motion, 

 the smaller flagellum being also rapidlv vibrated, the 



Figure 6. 



Figure 7 



Stages in division. 



Figure 8. Figure 9. 



Conjugation. The sac. 



Note. — .\1I the figures are niaiinificd one thousand times. 



Figure 10. 

 The sac dis- 

 charging yoimg. 



monad, and after a year and si-x months steadv w ork 

 on the form I have been able to accomplish m\- 

 object. 



This Monad is a long oval, or sausage-shaped, 

 organism, about one three-thousandth part of an inch 

 in length ; it posesses two flagella, one, the most 

 conspicuous, being long and curved, somewhat like 

 an eyelash, and the other being short and bent 

 somewhat sharply towards the body. The long 

 flagellum tapers towards the distal end, and becomes 

 like a whiplash ; the smaller flagellum is of the 

 same thickness throughout. .\ contractile vacuole is 

 present, situated about the middle of the organism. 



bod\' remaining motionless and apparent!}- adhering 

 to the slide. B\- means of these flagellar vibrations 

 currents are set up in the water towards the body of 

 the monad, and bacteria and other smaller monads 

 are swept towards the flagellar end of the organism. 

 On getting near, the long flagellum is often bent o\er 

 the other organism, which is thus guided to a point 

 between the two flagella. Here the currents 

 frequently cause the smaller monad or bacterium 

 to rotate rapidly for a time, till finally it gets 

 near the body of the monad. The protoplasm 

 then seems to flow out and completely engulfs 

 the smaller organism, and its body is passed 



436 



