THE STRUCTURE OF CRYPTOGONIMUS 
519 
seen. The oral sucker was kept commonly in a state of partial 
contraction. In some cases it was seen to be emploj^ed in the act 
of adhesion. The ventral suckers, especially the anterior one, 
occasionally were seen to be somewhat extended beyond the 
contour line of the body wall and then withdrawn. 
METHODvS 
Careful studies of the internal organization of the living material 
were made, with especial efforts to determine the anatomy of 
the excretory system, since no other method demonstrates the 
minute parts of this system as well. A certain degree of compres- 
sion which can be readily regulated by absorbing the water by 
means of little wedges of bibulous paper is favorable. After 
trematodes have been confined for some time the tissues become 
clearer and organs previously invisible can be seen. Many of 
the worms were separated out from the chyle and killed and fixed 
in aqueous corrosive sublimate solution. Some of these were 
stained in borax carmine and mounted whole in x^dol balsam, 
under a cover glass supported on rollers, made by drawing melted 
glass tubing out into threads. This method permits one to roll 
the animal over and view it in every position, and was found 
very useful. It is, however, to serial sections that we must turn 
for the most precise information of the organization of this small 
worm. Its minute size made it necessary to devise a method of 
imbedding in which records of the orientation were kept. This 
was done by pouring melted paraffine into a cold watch-glass under 
the simple microscope and then adding from a warmed pipette a 
drop of melted paraffine containing one of the infiltrated worms. 
As the worm gradually sank into the stratum of half congealed par- 
affine on the bottom of the watch-glass it could readily be adjusted 
in any desired position with a heated needle and held there a 
moment till the paraffine was cold enough to hold it in place. A 
mark on the surface of the paraffine sufficed to show the position 
of the worm within. Series were cut in the usual planes and 
stained on the slide in iron-haematoxylin. This reagent pro- 
duces very fine anatomical, and in some respects, cytological re- 
