Anatomical structure of Aspidogaster conchicola. 479 



of the organs and for adequate views of complex parts the latter is 

 particularly adapted. 



Heretofore the investigation has been pursued almost entirely in 

 the living animal which must be more or less compressed under the 

 cover-glass. The considerable size and rigidity of the ventral sucker 

 influences to a great degree the form of the compressed animal and 

 the more pliable and delicate parts are thrown out of position and 

 changed in apparent dimensions. 



Again, the ventral sucker and the entirely non-transparent in- 

 testine and vitellaria either overlie or underlie the other organs. On 

 the whole, the living Aspidogaster is in many respects a difficult 

 object. One requires to make numerous preparations and may, by 

 this means, chance to obtain the required parts free for observation. 

 Another way is to select animals at a period just previous to their 

 sexual maturity and by this means avoid the consequences of the 

 yolk-glands and ducts and the sexual ducts being filled with non- 

 transparent matter. And even with this precaution , which can only 

 meet with limited application, there are many difficulties. A glance 

 at a drawing of a cross section will indicate how incomplete must 

 be our view when the worm is compressed from side to side and 

 its organs pressed into one another in order to make it thin enough 

 for use under high powers of the microscope. 



In mounting the living animal, it was enclosed in a drop of 

 Anodon-blood, or physiological salt solution under a cover-glass sup- 

 ported on wax feet. Upon waiting a little time, the worm, in its 

 attempts to crawl, would expand its ventral sucker and straighten 

 out. Then, by sucking out a little of the fluid with blotting-paper, 

 the cover was gradually lowered until the desired compression was 

 reached. After this the cover was surrounded with a ring of wax. 

 This is easily done by highting a wax taper, holding it horizontally 

 to allow the wick to become saturated with melted wax, and then 

 blowing out the flame and drawing the end of the wick along the 

 edges of the cover-slip. In this state the animal will live for hours 

 — the length of time depending upon the degree of compression, 

 kind of fluid used, health of the animal etc., and the slide can be moved 

 about under the oil-immersion lens without fear of destroying the 

 preparation. This admirable method is the one used with great suc- 

 cess by Dr. Looss. 



In killing, hardening, and staining, I made use of numerous 



