THE MICROSCOPE. 197 
alcohol. After one or two hours they may be transferred to stronger 
alcohol. The best results have been attained by slowest increase, as 
passing at intervals of three hours through 60%, 70%, 80%, 90%, to 
95%, finally, in which they may be kept until wanted. If time and 
_ patience fail, the 60% and 90% may be omitted. 
When ready to prepare for sections, the worms may be cut into 
pieces, preferably such as will include certain regions of the body. 
For instance, the first seven segments will include the pharynx, the | 
second seven will have the reproductive organs, the third seven will 
have the crop and gizzard, and a portion of the stomach-intestine; 
any portion further back will show the peculiarities of the stomach- 
intestine. 
The pieces thus cut may be stained as a whole, or the imbedding 
may be first performed, and the sections stained upon the slide. For 
rapid work, staining in toto is to be preferred; by the other method 
a slightly sharper definition of some of the tissue elements may be 
secured. Double staining has not been tried. In the imbedding, 
the method first suggested, I believe, by Hoffmann, of placing the 
paraffin cup with the object in a vacuum has been tried, with good 
results. The usual method is to transfer the stained pieces to 
turpentine, leaving them until they have acquired a semi-transpar- 
ent appearance; then to turpentine having so much paraffin dissolved 
in it that it will remain liquid at a temperature of 30° C; thence to 
soft paraffin, finally to hard paraffin. 
The sections were cut either with the Bausch & Lomb micro- 
tome or with the Ryder automatic. A thickness of > 545 to qsyy of 
an inch gave very satisfactory results, In some regions, serial sec 
tions are almost indispensible, as, for instance, in the locality of the 
crop and gizzard. 
The section chosen for special description was cut from the 
neighborhood of the fortieth segment, and was taken because of its 
relative simplicity, and because it shows several features of much 
interest. The general form of the body in section is shown (Fig. 1) 
to be circular and somewhat flattened beneath. At four points upon 
the circumference the groups of sete protrude (s, Fig. 1). These 
groups are arranged in four longitudinal rows. The sete them- 
selves have the shape shown in Fig. 6. The musculature is so ar- 
ranged that the sete may be turned in any direction, forward or 
backward, up or down. They thus form reversible holdfasts by 
which the animal manages its progress either through the earth or 
in its tunnels. The groups are connected by internal muscles which 
cause them to work together (s m, Fig. 1). The microscope reveals 
- 
