AUXETIC ACTION ON SPORES OF A NEW SPECIES 



OF POLYTOMA. 



By AUBREY H. DREW. 



Author of " The Life History of a New Monad." 



Polytoma uvella was originally described by Ehrenberg, 

 and subsequently studied by Dallinger and Drysdale. 

 Saville Kent also did valuable work on this organism, 

 and described a variety differing from the type by the 

 possession of a red spot on the body, and conse- 

 quently called Polytoma ocella. Dr. Dallinger 

 referred to the organism as the Acorn Monad, and 

 he and Drysdale were able to complete its life-cvcle, 

 while Saville Kent also added to our knowledge in 

 this direction by showing that the knob-like appen- 

 dages at the roots of the flagella, as described by 

 Dallinger and Drysdale, were really in the nature of 

 loops. Since the work of these observers little more 

 has been done with regard to these organisms, nor 

 has any new variety been described. In Ma}', 1910, 

 I had the good fortune to examine some Monads 

 strongly resembling Polytoma uvella, and, indeed, at 

 that time I classified them as such ; but in February, 

 1911, 1 again came across the organism in a vegetable 

 infusion, and noting after careful examination some 

 peculiarities about it, I determined to study it further. 

 I discovered with comparative ease that the organism 

 was certainly a variety of Polytoma, as asexual 

 reproduction v vas a division into four ; and on care- 

 fully working out its life-cycle, I observed several 

 very striking differences from Polytoma uvella, thus 

 proving beyond a doubt that the organism was quite 

 a new one. On account of its very striking granular 

 appearance, I suggest that it should be named 

 Polytoma granulosa. (See Figure 103.) This organism 

 varies somewhat in size, but the average is between 

 one fifteen-hundredth to one twelve-hundredth of an 

 inch in length, the body is ovate, and is invested 

 with a distinct cuticle, enclosing uniformly granular 

 contents. A contractile vacuole is present, which is 

 situated at the anterior end. The flagella are two 

 in number, arising from the internal protoplasm, and 

 piercing the envelope. They are equal in length, 

 and exceed the body length of the monad. Occasion- 

 ally they are crossed over each other, giving the roots 

 a V-shaped aspect. Motion is rapid, but rather 

 irregular, the flagella being used as the arms are in 

 swimming, though the former are frequently not vibra- 

 ted synchronously; hence irregularity in motion arises. 

 The organism possesses a circular nucleus. This is 

 situated about the centre of the body, but in ordinary 

 individuals is invisible, owing to the granular contents. 

 The nutrition is apparently mainly saprophytic, 

 but is also holozoic at certain periods in the develop- 

 ment of the organism. Reproduction is interesting, 

 and takes place in the following manner. On study- 

 ing a normal form it will be found in the course of 



time that a slight constriction is appearing in the 

 granular sarcode, dividing the contents into two 

 equal parts. This constriction deepens, and the 

 contents retract somewhat at the equator of the 

 organism. Soon two spherical masses of protoplasm 

 are formed by this constriction. (See Figure 104;) 

 During this process the monad is usually actively 

 swimming, but now it generally comes to a standstill, 

 and fixes itself anterior end downwards on the slide, 

 and rapidly vibrates its flagella. Meanwhile each 

 divided half undergoes a similar process of division, 

 the fission this time being more or less transverse. 

 Soon four granular masses are formed within the 

 envelope, being arranged in a cruciform manner. 

 Motion now usually ceases, the flagella being cast off, 

 and the envelope with its contents alone remaining. 

 A delicate membranous cuticle now forms around 

 each of the products of fission, and minute flagella 

 are developed, which commence to vibrate. Finally 

 the separate organisms force their way out, leaving 

 the envelope behind them, the entire process 

 usually taking three or four hours. The method 

 of anisogamic reproduction is far more difficult to 

 ascertain, and requires careful and continuous obser- 

 vation over a length of time. If this condition is 

 complied with, it will be seen that sooner or later a 

 somewhat larger form in which the granular contents 

 have retracted from the posterior end, and with the 

 nucleus strongly developed, comes into contact with 

 a normal form. The two adhere by the posterior 

 ends, swimming being continued. (See Figure 106.) 

 In the course of an hour or two motion usually 

 ceases, both organisms adhering to the slide 

 while the flagella continue in vibration. In 

 about ten hours the two organisms gradually 

 melt together, forming an oval sac which slowly 

 becomes spherical. The sac is very granular and 

 shows the two vestiges of the envelopes, which 

 do not participate in the fusion. These vestiges are 

 as a rule washed away from the sac by currents in 

 the water, but occasionally persist adhering to it. 

 The sac remains in this condition for many days, 

 but it will be found that the contents are gradually 

 merging into one another, forming an irregular mass 

 of sarcode within. A constriction now appears in 

 this sarcode, and division slowly takes place, two 

 equal and slightly granular bodies of an oval 

 shape being formed. An envelope appears around 

 these organisms, and finally they acquire flagella, 

 and, after a varying period, they escape, leaving 

 the remnants of the sac. The completion of this 

 process takes from five to eight days. 



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