186 APPENDIX. 



these species are very different from P. aquilina in the shape of 

 the leaf and the habit of the stem. Alcoholic rhizomes furnish 

 excellent material for winter work, though fresh specimens are 

 preferable. 



In the lack of Pteris almost any fern will answer for study, 

 though close agreement with the text must not be looked for. 

 Asplenium, Aspidiuni, Adiantum, the wild maiden-hair fern (Adi- 

 antum pedatum) or Polypodium vulgare may be used. Directions 

 for practical study of Adiantum will be found in the Plant Dissec- 

 tion of Arthur, Barnes and Coulter (Holt, N. Y., 1886), and of 

 Aspidium in the Practical Botany of Bower and Vines (Macmil- 

 lan, 1885). Directions for procuring prothallia are given on p. 115. 



Luminous. Success in the practical study of the earthworm 

 depends very largely upon having large specimens properly preserved 

 by the simple method described below. If well preserved, earth- 

 worms are very satisfactory objects of study ; if not, they are worse 

 than useless. 



Large earthworms may be obtained in great numbers between 

 April and November, by searching for them at night with a lan- 

 tern, in localities where numerous castings show them to abound 

 (a rather heavy but rich soil will be found most productive). 

 They will then be found extended from their burrows, lying on the 

 surface of the ground, and may be seized with the fingers. Con- 

 siderable dexterity is needed, and it is necessary to tread very softly 

 or the worms take alarm and instantly withdraw into their burrows. 



For dissection both fresh and preserved specimens must be 

 used. Fresh specimens should be cautiously chloroformed under 

 a bell-glass (too long an exposure to the vapor or contact with the 

 liquid causes excessive contraction), then stretched out at full 

 length by pinning the fore and hind ends fast to a flat, wax-lined 

 vessel, opened by a shallow cut along the dorsal aspect, the flaps 

 pinned out, and the whole animal then covered with normal salt 

 solution or weak alcohol (40-50$). 



For preservation (every detail of which should be attended to) 

 a number of living worms are placed in a broad vessel filled to a 

 depth of about an inch with water. A little alcohol is then cau- 

 tiously dropped on the surface of the water at intervals of a few 

 minutes until the worms are stupefied and become perfectly motion- 

 less and relaxed (this may require three or four hours). They are 

 then transferred to a large shallow vessel containing just enough 

 50$ alcohol to cover them, and are carefully straightened out and 

 arranged side by side. After an hour the weak alcohol is replaced 



