1878.] the Life-History of a Minute Septic Organism. 335 



are in this condition, but they are continually freeing themselves and 

 swimming away and others are constantly coming. 



The changes now to be described will be understood to be given as 

 the result of long- continued and repeated effort. Failure is very 

 much more frequent than success in working out the preliminary 

 details, but pre-eminently so in steadily following to the end the 

 changes undergone by a minute organism.* I merely record the final 

 results, which have issued both from the study in detail of phases in 

 the life- cycle of the organism, such, for example, as the minutiae of 

 the method of fission and fusion — and also from an unbroken ob- 

 servation of its comparatively short life-cycle, which was three times 

 repeated. 



Following then, steadily, a normal form, which has just freed 

 itself from the springing condition, as fig. 1, the first real indication 

 of change, though by no means the first to be discovered, is a splitting 

 of the anterior flagellum, as seen at a and b, fig. 3, and the moving of 

 the nucleus to the centre, as seen at c. With a power of from three 

 to four thousand diameters, there may also be seen a delicate line under 

 the base of the flagellum, as shown at d. In the course of from 

 thirty to sixty seconds this has widely opened and the base of the 

 flagellum has divided as seen at a, fig. 4, while at the same time 

 the nucleus shows an incision in the direction of its length, as seen 

 at b in the same figure ; and a similar incision has commenced at the 

 posterior end of the body, as shown at c. In a very few seconds 

 more, this slight incision (c, fig. 4) is the origin of a wide opening, 

 as seen at <z, fig. 5, above which it will be seen that the nucleus has 

 almost divided and a pale line runs through the body- substance from 

 the upper to the lower opening. The posterior opening widens much 

 more rapidly than the anterior one, as fig. 6 shows, depicting a con- 

 dition ensuing in from one minute to four minutes after that shown in 

 fig. 5. And at this stage the nucleus has split into two and the 

 divided parts occupy distinct positions, as shown at a, b. The upper 

 or anterior split now widens as well as the posterior one, as shown in 

 fig. 7, leaving the two parts merely united by a neck of sarcode. 



* In fact hundreds are followed which from one or more of many causes do not 

 complete the cycle of their lives. It may be arrested — and frequently is — by death in 

 the ear her stages, in the middle, or stdl worse towards the end. In the same way 

 there may be failure by the individual form being lost amidst a crowd of others, or by 

 slowly working its way to the little ring of liquid at the edge of the "cover," and 

 then going out into it, and so making further study impossible. Or the apparatus 

 may be at a critical moment a source of trouble ; the delicate balance between the 

 moisture carried over by capillarity, into the chamber containing the fluid with its 

 organisms, and the evaporation taking place, may by some means, such as a sudden 

 change of temperature, be broken, and nullify hours of patient and, but for that, 

 successful work. In every such case there is but one method open— it is to begin 

 again de novo upon another form. 



