1887.] MICROSCOPICAL JOURNAL. 85 
first meets must be precisely parallel to the edge opposite. If these condi- 
tions have been observed, if the knife is sharp, and the paraffine is of the proper 
grade, slice after slice may be cut off the top of the prism, and the edges of 
successive slices will adhere together, so that a long narrow ribbon is formed, 
made up of the successive slices, all the slices lying in exactly similar posi- 
tion. A number of these slices can be mounted at the same time as easily 
as one slice. This makes it possible to preserve a long series of consecutive 
slices, and thus to trace any part through from section to section, and learn 
its shape and relations. 
12. In mounting it will be well to place a large number of sections on the 
same slide, and for the purpose, oblong covers, 2 inches long by { inch 
wide, may be bought of the opticians, or large sheets of cover-glass may be 
bought, and covers of any desired size cut with a writing diamond. If the 
series are cemented to the slide or cover before clearing off the turpentine, as 
many as 50 or 75 of a small object (say § in. square) can be mounted under 
a single cover. To fix the objects to the slide, spread over the slide a thin 
film of a mixture of 2 parts collodion and 1 part oil of cloves. Lay the sec- 
tions in rows as close together as you please upon this film, and lightly press 
them with a small camel’s-hair brush. Place them on a metallic surface warmed 
to 50° cent. for 15 minutes, then immerse the whole slide in pure spirits of tur- 
pentine ; the paraffine will be quickly dissolved. The turpentine must now be 
drained off as quickly as possible, and when the sections are almost at the 
point where, in another moment, they would become dry, a few drops of 
benzole or chloroform balsam dropped on the sections, and the cover-glass 
carefully applied. 
3. Examination of the sections.—1. Low power. As in the study of 
the organ, we are recommended first to become familiar with its most obvious 
features, so, in the study of sections, it is always wise to begin with a low 
power, and, after seeing all it will reveal, pick out certain parts from it for 
more detailed study. Figure t is a-:camera-lucida drawing taken from one 
of the sections, the one which passes through the place where the sack dips 
down into the glandular portion. 
a. The sack is shown below and to the left in figure 1, and the refer- 
ence letter S is placed in its cavity. Only a small portion of the sack was 
preserved and cut, the remainder being like it in structure. It is found to 
present an inner lining, the epithelium, which immediately surrounds ¢he 
cavity, and may be seen to be of noticeable thickness, and with dark spots at 
definite intervals along it. The cavity is seen to extend some distance into 
the substance of the gland, and the lining also to continue up into the space 
in the gland. This passage from the gland is called the duct. If the entire 
sack had been preserved, together with the tube leading out to the opening 
upon the basal joint of the antenna, it would be seen that the epithelium, 
which forms the lining of the sack, is continuous and without any break 
from the duct of the gland to the opening on the antenna, thus placing the 
cavity of the sack in direct communication with the outside water which 
bathes the body, and at the same time preventing water from entering at the 
opening and wandering about at large through the body within. A second 
layer may be seen to surround the epithelium, lining the sack ; it is a protec- 
tive and supporting covering for the epithelium. If this covering be followed 
to the gland, as was the epithelium, it will be seen that just where it reaches 
the gland surface it departs from the epithelium and runs around upon the 
surface of the gland, thus entirely enveloping both the sack and the glandular 
portion of the apparatus. 
6. The glandular portion is shown in figure 1 slightly simplified from 
the original section for the sake of clearness. The cavity of the duct is 
¢ 
