480 JOSEPH STAFFORD, 



combinations; but the best results were obtained from Flemming's 

 fluid, Hermann's fluid, Gilson's fluid, and a saturated alcoholic sub- 

 limate solution. The rest of the process was in short: wash; slowly 

 dehydrate in successive strengths of alcohol; gradually change from 

 absolute alcohol, by adding, at short intervals, in a small bottle, drop 

 by drop of pure benzole ; then in pure benzole ; benzole-paraffin ; 

 paraffin ; section ; stain on the slide in borax-carmine or haematoxylin ; 

 mount in Canada-balsam. 



External characters. 



The adult Aspidogaster is about 3 mm long and 1 mm broad, 

 but may be found much smaller than this and yet distended with 

 eggs and yolk. It is not flattened dorso-ventrally as so many Tre- 

 matodes are. When at rest in its normal position and most symmetrical 

 form it is somewhat anvil-shaped (Fig. 8) being supported by an 

 expanded ventral portion or "foot", above which is the cylindrical 

 body portion narrowing posteriorly into a rounded conical form, and 

 tapering anteriorly into the forwardly projecting neck. In front are 

 two projections (Fig. 3): the flattened end of the ventral foot; and 

 the cylindrical neck, terminated by a trumpet-shaped mouth opening. 

 Between the two, and extending backwards into the body , is a de- 

 pression which I shall for convenience call the cervico- pedal pit 

 (Fig. 3, 7). Behind, the foot with its underlying ventral sucker forms 

 a much closer union with the body, so that, here, there is seldom to 

 be seen any cleft separating ventral and dorsal portions. 



While the animal lives, it assumes this regular form for only 

 short periods. It is much more likely to exhibit an unlimited number 

 of changes in appearance, during which one or other of these parts 

 is contracted or extended, folded, wrinkled, contorted, or otherwise 

 modified in shape. The mouth end may protrude far beyond the 

 anterior end of the foot , sweep round in a circle as if feeling, turn 

 far back alongside of the body, or withdraw until it can not be 

 recognized. Frequently , too , it looses its funnel form and thickens 

 into an upper and a lower lip with the side - walls connecting these 

 thinned out so as to be much less visible. In a drop of water on a 

 slide or in a watch glass, the animal often fixes its ventral sucker 

 to the glass and then draws back its body and turns its neck to one 

 side so as to show at least half of the foot from above. A favorite 

 movement seems to be to intrude the anterior end of the foot into its 

 l)road trumpet mouth-opening, as if pressing something down its 



