1 





Dr. A. Gruber on Protozoa. 275 



for, leaving out of consideration the absence of a clothing with 

 the small bacilli, the two forms have a number of agreements 

 such as the tenacious consistence and slight mobility of the 

 protoplasm, the occurrence of numerous nucleiform corpuscles 

 in the interior, the enclosure in a fine firm layer of protoplasm 

 which, by a certain mode of preparation, stands forth like a 

 cuticle, the form of the pseudopodia, and finally the mode of 

 division. The only differences therefore are, that in one 

 form pseudopodial cones are always formed, and that in the 

 other the little bacilli of the skeleton are seated upon the 

 peripheral layer of sarcode. I would therefore regard the 

 last-mentioned Rhizopod only as another state of Pachymyxa. 



2. Amoeba obtecta. 



Besides the Pachymyxa just described ; I also found, in the 

 small marine aquarium of the Zoological Institute here, 

 another form of Rhizopod, and indeed an Amoeba, which 

 differs in many respects- from the other species of its genus ; 

 and I have named it Amoeba obtecta. It is very small, mea- 

 suring only 0*03-0*04 millim., and does not creep freely about, 

 but constructs a dwelling in which it conceals itself. As 

 regards the latter, it is formed of a mucous substance of yel- 

 lowish colour, which seems to harden more and more in water. 

 The innermost part of the envelope which lies nearest to the 

 Amoeba is the firmest and the darkest-coloured ; it forms the 

 true carapace, while around it may lie an irregular zone of the 

 yellowish substance, to which numerous granules and other 

 foreign bodies firmly adhere. 



In composition and coloration the substance of the envelope 

 exactly resembles that which I have described in Sticho- 

 ■ tricha socialis*. As regards its form, the carapace is basin- 

 shaped (fig. 5) ; t. e. it possesses a rounded bottom and a wide 

 aperture for the issue of the protoplasm. Frequently one half 

 of the side wall has not been developed ; and then the Amoeba 

 lies rather loosely in a simple saucer. The protoplasmic body 

 which shelters itself in this envelope shows nothing remarkable 

 that would distinguish it from the allied species of Amoeba. 

 The sarcode is tolerably tenacious and immobile, although 

 far less so than in Pachymyxa. The portion that lies in the 

 bottom of the basin is finely granular and turbid, while the 

 opposite end, situated at the aperture, is clear, and appears 

 formed of a hyaline mass. The pseudopodia originate from 

 this ; but I have only rarely been able to observe them, as the 

 Amcebce do not readily recover from the disturbances which 



u Xeue Infusorieu," Zeitschr. fiir wis-. ZooL Bd. xxxiii. 



19* 



