208 APPENDIX. 



out evenly on a slide and dried cautiously over a flame. Stain 

 with haematoxylin for three minutes ; wash thoroughly with water, 

 add strong aqueous solution of eosin, allow to stand one minute ; 

 wash this time very rapidly, remove the excess of water quickly 

 with filter-paper pressed down over the whole slide ; dry rapidly, 

 and examine with low power. If successful mount in balsam ; if 

 the specimen is not pink enough add more eosin and wash still 

 more rapidly than before. In good specimens the cells keep 

 their form perfectly, the cytoplasm is bright pink, and the nucleo- 

 plasm is light purple. 



Epidermis from young leaves of hot-house lilies (" African ' 

 lily, "Chinese' lily, and especially lily- of -the- valley) yields 

 cells showing finely the cell-wall, nucleus, and (in favorable 

 cases) cytoplasm. If stained with acetic acid and methyl-green 

 the nuclei are highly colored; with Delafield's lisematoxylin the 

 cytoplasm is more easily seen. 



Cell-divisions or Cleavage are easily observed in segmenting 

 ova or in fresh specimens of Protococcus (Pleurococcus) de- 

 tached from moistened pieces of bark which bear these algae. 

 (See p. ITS). 



Stages in the cleavage of the ovum may be seen in the seg- 

 menting eggs of fresh-water snails (Physa, Planorbis] which 

 are easily procured at almost any time by keeping the animals in 

 aquaria. The old egg- masses should be removed so as to ensure 

 the egs;s being fresh. Or a supply of preserved segmenting eggs 

 (star-fish, sea-urchin) may be kept for demonstrating the early 

 stages. 



Protoplasm in Motion. The best introduction to protoplasm 

 in motion is afforded by a superficial examination of Amoeba 

 (for procuring Amoeba see above, Chapter XII). If Amoeba is 

 not available young living tips of Nitella or Chara may be used. 

 Anacharis and Tradescantia are useful, and often very beautiful, 

 but less easy to manage, as a rule. In mounting Nitella or 

 Chara care must be taken not to crush the cells, and as far as 

 possible pale fresh specimens rather than darker and older ones 

 should be chosen. If Anacharis is to be studied the youngest 



leaves should be selected from the budding ends, and not, as is 



~ * 



sometimes recommended, leaves which are becoming yellow. 

 The movement in the cells of Anacharis leaves often begins 



