Contractile Vacuoles 



471 



A large vacuole, or a group of contributary globules, freed into 

 the water by ripping open a cell under slight pressure, retain 

 their identity in this medium for some time. A quick upward 

 thrust of a blunt needle against a large vacuole apparently causes 

 its rupture into the surrounding endoplasm, for an increase in 

 fluidity is observed in this area. This would imply the misci- 

 bility of vacuolar fluid and endoplasm. 



The contractile vacuoles of Paramecium caudatum become 

 dilated on the addition of Grubler's Alizarin blue to the cul- 

 ture. The distended vacuoles together with their feeders become 

 set, gradually taking on a vivid blue color. This stain is specific 

 for the vacuolar walls, and, although it appears long before 

 ciliary action ceases, should be classified as a sub-mortem rather 

 than a vital stain. These stained and distended vacuoles do not 

 collapse when removed from the animal but retain their shape 

 and may be manipulated and dissected with microneedles. 



The complete paper will appear in the Journal of Experi- 

 mental Zoology. 



234 (2194) 



Notes on the dissection of amoeba verrucosa. 



By RUTH B. HOWLAND (by invitation). 



[From Cornell University Medical School, New York City.] 



The specific structure and characteristic properties of the pel- 

 licle of Amoeba verrucosa may be demonstrated in the living 

 animals by means of microdissection and injection. A high de- 

 gree of resistance to mechanical pressure is exhibited by the 

 pellicle when subjected to compression. Perforation of the 

 pellicle without indentation of this layer can be effected only 

 with needles having extremely fine points. Withdrawal of a 

 needle after penetration carries the pellicle out into a long cone- 

 shaped process, loss of endoplasm being prevented by the rapid 

 formation of a restricting endoplasmic film at the base of this 

 cone. Distortion of the pellicle due to compression or other 

 injury persists for some time before the membrane resumes its 



