a Lesson in Biogenesis. 55 



them were dividing by fission in a manner, as far as we know, 

 before unobserved, as drawn at c, c. We now made them the 

 special objects of attention, directing our examination first to their 

 mode of division. The first indication that it was about to take 

 place was, that the body became squarer, more plastic, and sub- 

 amoeboid, a slight but sudden constriction of the sarcode ensued, as 

 seen in Fig. 1, Plate XXV. ; this rapidly proceeded to the greater 

 constriction shown in Fig. 2. At this stage a stretching of the 

 constricted portion of the sarcode took place, as in Fig. 8, the 

 flagella a and h lashing with great force. As the sarcode stretched 

 it became finer, no more being extruded from the now perfectly- 

 divided bodies. In Fig. 4 it is drawn with the sarcode slightly 

 thicker than the flagella, and in Fig. 5 it has reached its final 

 length, after which, by the rapid and strong motion of a from h, 

 the attenuated sarcode c snaps at c, as in Fig. (J, leaving the sepa- 

 rated bodies a and h free, and each possessed of a new flagellum c, d. 

 Taking an average of forty cases, we find that this entire process 

 is completed in four minutes and forty seconds. 



Now becomes manifest the importance of continuous and patient 

 watching ; for we found that this mode of increase might continue 

 without any change whatever for eight days at least. But this is 

 a sufficiently long period to justify an observer in concluding that 

 it was the only mode by which increase was secured. If we Lad 

 not been constantly watching the other form in the same field, we 

 might have arrived at this conclusion, but our attention was at 

 length called to a new phenomenon. Many of the organisms in 

 question all at once appeared to be pouring out a delicate sarcode, 

 as in Fig. 7, a, h, Plate XXV. Nevertheless, they moved with great 

 freedom, and the flagella rapidly vibrated. This sarcode increased in 

 size all round the organism, but was of extreme tenuity, and as it in- 

 creased in quantity the latter moved only by pseudo-podia, although 

 the flagella were still comparatively active. In the course of seven 

 houis there were several in the field, moving in all directions, and 

 at length two approached and touched each other, as in Fig. 8, 

 Plate XXV. ; a rapid blending of the sarcode now ensued, and the 

 flagella disappeared : they were constantly watched ; the amoeboid 

 sarcode of each blended with the other, and at length the bodies 

 touched and began to unite, as in Fig. 9, Plate XXV. Their union 

 was now rapid until it reached the condition drawn in Fig. 10, 

 Plate XXV., and at length it became a mere cyst, figured at 

 Fig. 11, Plate XXV., with a very decided investment. Having 

 reached this condition and become slightly yellow in hue, an appa- 

 rent thinning of the integument of the cyst ensued, and it became 

 suddenly rent all round, and retracted towards the centre, as in 

 Fig. 11, I'lute XXIV. Up to this time we had employed without 

 intermission a magnifying power of 2500 diameters. (Powell and 



F 2 



