274 Dr. A. Gruber on Protozoa. 



which is furnished with an envelope, there exists an ex- 

 tremely fine layer of protoplasm as a coating over the whole 

 body. I have previously asserted* that in all Khizopoda the 

 outer limit of the protoplasm acquires a different consistency 

 by contact with the water, and that the flow of an Amoeba 

 or of a pseudopodium consists in a continuous breaking 

 through this external membraniform layer on the part of 

 the fluid sarcode yielding to a pressure, during which this 

 layer is constantly being formed anew. 



In most Khizopoda this is not to be seen ; and even in the 

 resent case we perceive nothing of it in the living animal, 

 ut this sort of cuticle is shown only the more distinctly by 

 the application of reagents. Thus, if we kill the Rhizopods 

 with osmic acid, stain them with carmine, and mount them 

 in Canada balsam, the protoplasm contracts, and we see a 

 fine membrane separated from it and reproducing its contour. 

 If the preparation is successful, the pseudopodial cones with 

 the pseudopodia themselves are preserved. In the fine mem- 

 brane we then see very distinctly elevations at many points, 

 each corresponding to a subjacent cone — a proof that the mem- 

 brane, as a delicate layer, has enveloped the cones also, and 

 been perforated by the pseudopodia. Here also I could never 

 detect a nucleus ; but with proper preparation and staining 

 there appeared the same numerous red granules in the interior 

 as in Pachymyoca. As in this, also, reproduction by division 

 appears to be frequent. 



The next question is where, from the characters described, 

 we have to seek the allies of this Ehizopod. The most obvi- 

 ous course, perhaps, is to regard it as identical with Amatba 

 tentaculata, which I also discovered at the same spot in our 

 marine aquarium. Size cannot come into consideration in 

 the comparison, as it is very variable in the different speci- 

 mens; on the other hand, the phenomena of movement in 

 Amoeba tentacvlatawere quite different. The stao-e in which 



£3 



it emitted the pseudopodia described only represented arestin w 

 state, whereas otherwise it could pass into a constant flow, just 

 like other Am&bce, especially Amoeba quadvilineata ; moreover 

 it possessed a distinctly visible typically formed cell-nucleus, 

 both things which never came under observation here. It 

 might indeed be assumed that this Rhizopod is a developmental 



stage ot that Am&ba, but this is very improbable. 



But as regards the connexion of the form under consider- 

 ation with the above-described Pachymyxa, the supposition 

 seems almost inevitable that it is identical with the latter; 



* Loc. cit. supra. 



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