286 Transactions of the Society. 



with small punctuations ; a typical Infusorian nucleus, but near 

 which I could not ascertain the presence of a micronucleus. In one 

 of the individuals, however, I thought I could distinctly see it, and 

 in fig. 1 this micronucleus has been represented ; but this small 

 spherical body, which I could not detect in either of the other 

 specimens, may not be necessarily a microjiucleus. All the 

 individuals, in fact, treated with carmine after sufficient observation 

 in vivo, coloured rather intensively in their entire mass, and if the 

 nucleus itself was very distinctly delineated and easy to recognize 

 as such, the small roundish body which was seen close by in one 

 of the specimens might have simply been one of several other 

 small red bodies without any particular significance, disseminated 

 in the cytoplasm. 



Up to this, Arachyiidioims faradoxa does not present any 

 particular features which might distinguish it from other Infusoria ; 

 but we must now speak of the locomotive or vibrating organs, 

 which are here absolutely different from anything we know. In 

 fact, we have here, not cilia nor cirrhi nor undulating membranes 

 or lamellae, but tubes, or what we might call genuine tentacula. 

 Of these there are two, both of which start from a common basis, 

 from a broad fissure-like opening at the anterior part of the body, 

 rounded at both ends and somewhat constricted in the middle 

 (fig. 3). This opening — if we may apply that term to it, for it has 

 surely no real analogy with a " mouth " — is filled with a clear 

 substance which projects outside like a cushion ; and from it 

 diverge in opposite directions two " tentacles," transparent, very 

 pure and opalescent in appearance, rounded or perhaps slightly 

 elliptical in transverse section, broad at the base and gradually 

 tapering to a pointed extremity. They are very long, and when in 

 a state of repose are seen to be trailing to half the distance behind 

 the posterior extremity of the animalcule, left and right of what 

 might be called either the dorsal or ventral face of the body. Fig. 1 

 shows this particular disposition of the tentacles, with their 

 common cushion-like basis ; in fig. 2, where the animalcule is 

 supposed to be seen from what one might call the side, with an 

 orientation at an angle of 90° to the first, the enveloping pellicle 

 or film — if there is one at all— is seen to be somewhat excavated 

 at the root of the tentacles. 



The tentacles, however, are rarely seen as fig. 1 represents 

 them — i.e. in the state of rest. The intervals of rest last only for a 

 very short time, a few seconds at most ; then the tentacles lift up, 

 develop a graceful curve, somewhat like that of the horns of a ram 

 (fig. 3, where the animalcule is seen from above, along the longi- 

 tudinal axis of the body), describing a spiral downwards ; and both 

 horns begin vibrating, beating the water with such a rapidity that 

 the shape of the horns disappears from sight to give the impression 

 of a whirling body. 



