Septembkk, 1912. 



KNOWLEDGE. 



FlGUKl 



had to the "Camera Lucida." Movement may 

 be stopped by very dilute solutions of cocaine 

 hydrochlorate. The drawings illustrating the life 

 histor\- of the monad herein described were done bv 

 means of a Camera Lucida and Watson's " Holo- 

 scopic Immersion Paraboloid " which gives excellent 

 dark-ground effects with high-apertured lenses. 

 XMiilst engaged in working out the life history of 

 the Moiii7s sarcopha^ci I 

 frequently observed small 

 organisms somewhat resem- 

 bling this monad, but of con- 

 siderably less size and possessed 

 of a peculiar jerky motion in 

 swimming. 



FiGUKK i()(). 



First stage in formatioi 

 of sac. 



life history were not 

 a few, but at length 

 I have been able to 



accomplish it. This gecond stage in form 

 monad is an entirely tion of sac. 



new one, and on 



account of its peculiar \ibrator\- motion 

 in swimming I have named it Moiilis 

 vihi\iiis. This organism is closely related 

 to. and belongs to the same sub-tribe as 

 the Moiias sarcophaga, viz., the Para- 

 mastigoda. It varies slightly in size, but not nearly 

 so much as the Moiias sarcophaga, the average 

 size being about one four-thousandth of an inch in 

 length. The shape is blunth" triangular or conical, 

 and the organism is very granular. It possesses two 

 flagella. one long and one short (hence Para- 

 mastigote). The long tlagellum is not as long in pro- 

 portion to the bodv as that of the Monas sarcophaga, 

 and is bent round somewhat like a fish hook ; the 

 small flagellum, which is e.xceedingly minute, and 

 generally rather difficult to observe, arises from the 

 base of the long one, and on its convex side (see 

 Figure 360). A nucleus, which stains somewhat 

 irregularly with Haematoxylin, and a contractile 

 vacuole are present. Swimming occurs by lashing of 

 the long tlagellum, aided by the smaller one. The 

 long flagellum is vibrated with a peculiar whip-like 

 motion which makes swimming very jerky and 

 irregular. On following one of these forms by 

 means of the mechanical stage, never losing sight of 

 it in all its \\anderihgs, it is found after a varying 

 period to come to a standstill, and to adhere to the 

 slide, apparently by means of a pseudopodial appen- 

 dage. On coming to a rest, the long flagellum is 

 vibrated with great rapidity, thus causing small 

 protoplasmic particles and bacteria to be swept 

 tosvards the monad, many of which on touching 

 the body, near the ftagella. are engulfed by an 

 amoeboid action of the protoplasm. This stage of 

 feeding niav last for hours ; in fact, the monad 



Figure 368. 

 Sac discharging spores 



spends a large part of its existence in feeding in 

 this way, swimming about at intervals apparently 

 in search of pastures new. .\fter some time two 

 new flagella slowly appear near the normal pair. 

 .\t first, these are very minute but rapidly grow 

 larger and are in intense vibration ; they swiftly 

 diverge and at length get to the opposite pole to the 

 normal pair. During this duplication of the flagella, 

 the nucleus of the organism has become strongly 

 developed and a division takes place ; one of the 

 two daughter nuclei now passes into each polar 

 region, and with the two pairs of flagella now pulling 

 from opposite ends a constriction suddenly appears 

 across the body of the monad. From this time 

 onward the constriction rapidly deepens, the two 

 pairs of flagella pulling the organism into an hour- 

 glass shape, shown in Figure 363. Finally, only an 

 exquisitely-fine strand of protoplasm connects the 

 two babes; this strand graduall)- gets thinner till at 

 th it snaps, and the two organisms go free. Usually 

 one of the two remains in the place where 

 division took place, and at once commences 

 to feed, while the other swims about for a 

 time, till it also becomes stationary, and 

 commences feeding operations. In a few 

 instances I have observed feeding to 

 go on during the 

 actual process of 

 division. The time 

 occupied in this 

 division is usually 

 from fifteen to tw enty 



Figure 369. 



m 1 n u t e s . 

 For man\- 

 m o n tjh s 

 this was 



the onlv r- n r u 



1 J 'r Spores after four hours 

 metriod ot growth, 



reproduc- 

 tion which I could observe. 

 At length, however, I found 

 that a certain proportion of the Figure 370. 



organisms, after swimming and Sedentary form feeding, 

 feeding in the manner already 



described for man\' hours, became very sluggish 

 and usually sank to the bottom of the drop of 

 of fluid under examination : the flagella lashed feebl\-, 

 and the bod\' of the monad became very pale and 

 rather indistinct, the nucleus becoming considerably 

 more prominent than usual and situated towards the 

 posterior end of the monad. In several specimens 

 I have noticed that the nucleus became somewhat 

 striated at this stage. Finally, the flagella ceased 

 movement, and the whole organism was perfecth- 

 motionless. .At first, I came to the conclusion that 

 some deleterious influence had killed the monad, and 

 it was only after I had again and again failed to find 

 any other method of reproduction than the asexual, 

 that I determined to study these motionless forms 

 further. A peculiarity of this monad is the 

 length of time that it may remain in this quiescent 

 condition. In four specimens I observed the average 



