272 Mr. J. T. Arlidge on some of the Phases of Development 



itself a hollow in its wall (fig. 8) . Moreover, the rotatory mo- 

 tion became very slow and feeble, and although the external 

 large cilia still flapped, bending towards the left, no motion oc- 

 curred in that direction, save a slight oscillation of the lower 

 half ; whilst the motion of the inner mass was irregular and 

 slow. 



During the next quarter of an hour, the animalcule went on 

 enlarging where occupied by the growing cells, the primary one, 

 now spherical, protruding strongly : and, by reason of this cell 

 having now nearly equalled in size the original being, the whole 

 appeared like an animalcule in process of transverse fission (fig. 9) . 



The second cell, which previously had occupied rather a lateral 

 position with reference to the primary one, was now situated 

 almost entirely beneath it. This second and smaller cell also 

 was the only one which could be properly said to be included 

 within the parent form, the larger one being but an appendage. 

 The only portion which would seem to retain the latter in situ, 

 was one — containing granular matter and some globules like the 

 rest of the parent substance, — extending upwards for a short 

 distance as a lateral band. 



The revolution of the animal seemed now to cease for a little 

 while, but presently was resumed feebly and irregularly ; the ex- 

 ternal ciHa however only causing a jerking movement of the 

 lower part. 



During the later changes, the cilia, which primarily fringed 

 the entire margin, were now seen on the lower one — that viz. 

 which remained of the original periphery — and also, owing to the 

 transparency of the animal, along a line behind and just below 

 that along which fission was about to occur (fig. 9). 



At seven o^clock, the lateral band attaching the budding cell 

 to its parent had retracted to within a little distance of its base : 

 the growth of the second cell had much advanced, and by its 

 upward pressure against the primary sac, and the lateral pressure 

 of the walls of the parent animal, it had assumed an irregular 

 shape ; but its cavity remained quite diaphanous, excepting in its 

 lower part, where a few fine granules were dispersed (fig. 10). 



On one side of the two developing cells a small transparent 

 globule existed, along with three or four others, and some amor- 

 phous particles, in the substance of the parent being. The cilia 

 had apparently decreased in size — or at least in distinctness and 

 energy, and at half-past seven they had disappeared, motion in 

 them having previously been arrested (fig. 10). 



At about a quarter to eight o'clock p.m. the first-formed cell 

 had rendered itself almost independent of its parent, and was 

 bent to one side. The second sac had much increased in size 

 (fig. 11). 



Having withdrawn my attention for a moment to complete the 



