IN CYPRIS CIXEREA. 245 



coagulated. I then tried warm nitric acid. It would be weari- 

 some to relate my many attempts and failures, but at last I was 

 enabled to produce the perfect head or scolex, and to watch under 

 my instrument the progress and escape of it through the invagi- 

 nated portion of the cyst. The following was my modus operandi : 



The Cypris is placed on a glass plate with a drop of water, 

 then crushed, and the cysticercooids freed from the debris^ a drop 

 of nitric acid being added. The glass plate is then'held over the 

 chimney of a lamp until the small quantity of liquid begins to 

 simmer. It is then removed and allowed to cool for a few seconds, 

 then placed on the stage of the microscope, and examined either 

 with a 2-in. or i-in. objective. The former is preferable, as it does 

 not dull or become affected by the fumes of the warm acid. 

 Little change will be visible at this the preliminary step, but it 

 enables one after a few trials to judge of the length of time for the 

 next process, which is to add another drop of acid and to again 

 subject it to the simmering process. If then it is removed to the 

 stage of the microscope and examined, it will be seen that a great 

 change has taken place. That which before appeared to'^be a 

 structureless mass of plasma has now become a solid, dark-brown 

 mass, and at the invaginated end of the cyst papilla-like pro- 

 tuberances have begun to form (Fig. 4, a). This is caused by the 

 invaginated portion of the cyst being pushed upwards, owing to 

 the development of the embryonic head. This continues to swell 

 and form a dome, and then the watery secretive fluid, spoken of 

 above, which exists between the space which bounds the inner 

 wall of cyst and the investing membrane of the head is emitted 

 from the centre of the dome and flows out in a steady upward 

 stream. It floats away like a flocculent cloud in the surrounding 

 liquid, and quickly becomes absorbed. I have tried to devise 

 means for arresting it for examination, but have not succeeded. 



The escape of this fluid has caused a great change to take 

 place within the cyst. The scolex has become more defined, and 

 with the circlet of hooks has begun to move in an upward direc- 

 tion. Instead of lying in a circle they have become oval, owing 

 to the pressure of the formative tissue, and are now vertical to the 

 polar axis of the cyst (see Fig. 5, c)^ the whole mass pushing up 

 the dome-like portion of the cyst until it forms a bladder of a 



