A New Type of Infusorian : Arachnidiopsis paradoxa. 285 



its anterior part, and pointed posteriorly (fig. 1). Yet this pointed 

 extremity may be wanting, according to the moment of the 

 oljservation, to reappear a moment after ; or, on the other hand, 

 this posterior part may terminate in a kind of lobe or knob of 

 transparent protoplasm, whose presence will be ephemeral also 

 (fig. 2). In short, this posterior region is somewhat changing, 

 amceboid, and at the same time somewhat glutinous. Very likely 

 this terminal point is able to keep the animalcule in place, affixing 

 it to some support, as I could on several occasions see it remain 

 quiet, wliilst the locomotory organs were vibrating actively. 



Except this particular region, the body is hardly deformable, 

 and keeps indefinitely its ovoid shape, in spite of the fact that the 

 animal seems to be naked, without any indication of a cuticle ; 

 should this latter exist, it would at any rate not be more than a 

 very thin film. 



There are no traces of strict, nor of cilia. However, the surface 

 of the body cannot be called absolutely smooth ; it shows rather a 

 rough appearance, and seems to be covered with very fine scattered 

 asperities ; and I could satisfy myself that these appearances are 

 in fact due to very fine rod-like particles, which are located under 

 the superficial film and press it out somewhat. 



The possession of these particles, in fact, is one of the charac- 

 teristics of the cytoplasm in our Arachnidiopsis ; they are dis- 

 seminated everywhere in the body, very fine as a rule, and mixed 

 with small round granules. At the anterior part of the body these 

 particles are much more densely accumulated, forming there a 

 blackish zone, and showing in their mutual arrangement a vaguely 

 radiating disposition around a clear and central surface which might 

 be taken for the oral aperture, but, as we shall see later, is some- 

 thing different in reality (fig. 3). 



Inside the cytoplasm one can also detect the presence — very 

 likely quite normal, as it could be verified in all the specimens 

 observed — of a big spherical body, which at first sight might be 

 regarded as a nucleus, but which in fact is nothing else than 

 an accumulation of these small rod-like particles, united together 

 into a mucilaginous pellet. 



In short, all these small rod -like bodies may be considered 

 as very finely divided food-particles, and nothing prevents us sur- 

 mising that the big spherical bodies themselves are nothing but an 

 accumulation of useless refuse, wdiich will be later eliminated. 



The contractile vesicle, rather large and active, is at the posterior 

 extremity. Sometimes, when in the state of maximal expansion, it 

 is seen to project beyond the surface of the body ; after the systole, it 

 forms itself again with the help of several lateral vesicles which 

 open in the central one. 



The nucleus, about the middle of the body and somewhat 

 laterally located, is sjjherical, relatively small, uniformly covered 



