GENUS OUEAMCEBA— OUKAMCEBA VOEAX. 69 



trailing longitudinally behind the body, as seen in figs. 1-9, pi. IX. Each 

 tuft is composed of from a pair to six or more filaments emanating from a 

 common point or stem, from which they divide and more or less diverge. 

 The filaments are of variable length, not only in the same individual, but 

 also proportionately with the body in different individuals. Sometimes 

 they are few and short or long ; more frequently they are numerous and 

 as long as the body or longer. They are straight, curved, and often irreg- 

 ularly bent ; cylindrical and blunt, or sometimes acute or swollen at the 

 end. They are mostly simple from their point of origin, but sometimes 

 branch off from near the latter, and rarely elsewhere. Sometimes an indi- 

 vidual is seen in which the filaments appear irregularly contracted at one 

 or more points, and bent or twisted, as if in these positions they had been 

 injured and become atrophied, as represented in fig. 5. 



In structure, the caudal filaments of Ouramccba vorax consist of a color- 

 less membranous tube with pale granular contents, mingled with a variable 

 proportion of oil-like molecules. The latter sometimes increase to consid- 

 erable drops elongated in the course of the enclosing tube. (Fig. 12.) 



The mode of fixation of the caudal filaments is difficult to comprehend. 

 In a detached tuft, the root appeared to be continuous with a ball of homo- 

 geneous protoplasm, as seen in fig. 11. 



In the movements of Ouramceba, the caudal filaments are entirely 

 passive, and are usually dragged along behind it. Sometimes in varied 

 movements of the animal, the tufts of filaments become more or less sepa- 

 rated at their root to a greater distance than usual, and widely diverge 

 from one another, as represented in figs 2, 3. 



The caudal filaments present so much resemblance to the mycelial 

 threads of fungi, that I have suspected they may be of this nature, and 

 parasitic in character, dae to the germination of spores which had been 

 swallowed as food. I have repeatedly recognized, among the food of various 

 Amcebas, different kinds of fungus-spores, and it is not unlikely that these 

 lowly creatures may be infested with fungus-parasites, just as we frequently 

 find to be the case with insects. Even the constancy in the extension of the 

 filaments from a particular part of the body is no objection to the conjecture, 

 for in insects we observe certain species of Sphreria growing as constantly 

 from the head. There is, however, perhaps an important objection to this 

 view, and that is, the caudal filaments do not grow from a mycelium within 

 the protoplasmic mass of the body of the animal. 



