NOTES AND MEMORANDA. 305 



became rather more refractive, and the number of granules 

 within diminished considerably, whilst new particles after a 

 time seemed gradually to appear in what was now a mass of 

 contractile protoplasm. These new particles were at first 

 sparingly scattered, though as they were evolved they con- 

 tinued to grow into biscuit-shaped bodies, which sometimes 

 attained the size of -^~^^-^J-^" . All sizes were distinguishable; 

 and many of them moved slowly amongst one another, owing 

 to the irregular contractions of the semifluid protoplasm in 

 which they were imbedded. Gradually the number of ho- 

 mogeneous biscuit-shaped particles increased, and at last a 

 large vacuole slowly appeared in some portion of the embryo. 

 It lasted for about half a minute, disappeared, and then, after 

 a similar interval, slowly reappeared. Much irregularity, 

 however, was observed in this respect. The next change 

 that occurred was the complete separation of the embryo from 

 the cyst which it filled, and the commencement of slow axial 

 rotations. These rotations gradually became more rapid, 

 though they were not always in one direction. The mass 

 became more and more densely filled with the large biscuit- 

 shaped particles, and at last the presence of cilia could he 

 distinctly recognised on one portion of the revolving embryo. 

 Then, as M. Pouchet stated, the movements grew more and 

 more irregular and impulsive, so as at last to lead to the rup- 

 ture of the thin wall of the cyst — when the embryo emerged 

 as a ciliated and somewhat pear-shaped sac, provided with a 



large contractile vesicle at its posterior extremity On 



emerging from the cyst, all the embryos, although differing 

 somewhat in size, were of the same shape. This closely cor- 

 responded with the description given of Paramecium colpoda 

 in Pritchard's ' Infusoria,' namely, ' Obovate, slightly com- 

 pressed ; ends obtuse, the anterior attenuated and slightly 

 bent like a hook.' Cilia existed over the whole body, though 

 they were largest and most numerous about the anterior 

 extremity. No trace of an actual buccal cleft could be de- 

 tected ; and (except in the posterior portion of the body, 

 where a large and very persistent vacuole was situated) the 

 organism was everywhere densely packed with the large, 

 homogeneous, biscuit-shaped particles. For many days these 

 most active Infusoria seemed to undergo little change, though 

 afterwards the number of the contained particles gradually 

 began to diminish, whilst the body became more and more 

 regularly ovoid, and a faint appearance of longitudinal stria- 

 tion manifested itself, more especially over its anterior half. 

 At the same time a very faint and almost imperceptible mass 

 (' nucleus') began to appear near the centre of the organism ; 



