33S NATURAL HISTORY. 



reversing it, through those most highly organised, with nucleus and special vesicle, to those that 

 appear to have only a nucleus, and then to such as have neither. 



Professor Schulze and Dr. Hertwig believe that they have discovered a nucleus in. Foraminifera ; 

 and some of their examples, at first sight, are very striking. The presence, however, of other enclo- 

 plasts in recent specimens, and the possible artificial production of nuclear bodies in sarcode by 

 re-agents, still keep our doubts alive ; and Dr. Wallich is not yet inclined to alter his views as 

 conveyed in the foregoing sketch of his system. 



VIII. Beginning with Amoeba, essentially the best-organised of the Rhizopods, we have A. 

 proteus (Figs. 1, 3). Its name was founded on Linne's catalogue of organic beings in. the later 

 editions of his " Systema Natune," and on the still earlier appellation of " the little Proteus,"* given 

 by Rosel, in 1755, to this animalcule long before its real nature was understood. It is also known as 

 princeps, having this name in Ehrenberg's magnificent work on Infusoria, itc. It was referred to as 

 Proteus (Kffluens by Miiller in 1786 ; and this would have been an appropriate name for this 

 changeably spreading creature, but " Proteus " had already been used generically for the little cave- 

 dwelling amphibian of Adelsberg, and a new specific name was not wanted. See Dr. Leidy's concise 

 and clear history of the nomenclature of this and other Amoeba? in his " Fresh- water Rhizopods of 

 North America." 



There ai*e several varieties of A. proteus, one of which Prof. P. Martin Duncan has observed to 

 habitually form only blunt or short lumpy pseudopods, but to move flowingly along quickly, with 

 constant change of form, between nearly globular and somewhat cylindrical shapes. In time it 

 becomes quiescent and round ; and after parting with some of its contents, chiefly relics of food, it 

 becomes encysted, and then bursts, giving birth to crowds of young individuals. 



Another kind keeps its general outline more persistently than the other, but still creeps flowingly 

 until a change comes, when it puts forth pseudopodial processes, and roams freely about, but after- 

 wards attains an hibernating or quiescent stage. Having been shut up awhile in a closed membrane, 

 like the other, it ultimately swarms with zoospores inside, and then they escape through the breaking 

 of the capsule. 



In its different stages A. proteus has been seen to vary in size and shape from globular 0-2 

 millimetre across, through ovoid 0-3 by 0-15 millim., dendroid 0-5 by 04, palmate 0-5 by 0-35, radiate 

 0-2 and - 5 by 04, and cylindroid 1 millimetre long. The largest observed by Dr. Leidy 

 occupied a space of 0-6 by 0'2 and 0-35 millim. 



IX. One particular kind of Amoeba, which always has a tufted and knob-like extremity 

 to its food-carrying, coarsely granular hinder moiety, has been named A. villosa by Dr. G. 0. Wallich, 

 who has especially studied, described, and illustrated the life-history of this and many other species of 

 these Protozoa. A. proteus sometimes has a collection of little knobs or blunt papilla? (pimples) on 

 its hinder end (see Fig. 3) ; but this other Amoeba has always a villose or hairy ball-like end, with a 

 narrow neck-like connection to the body. It begins as a small circular hairy patch, and is 

 apparently sticky and prehensile, being often clogged with dirt. 



This Amoeba does not use pseudopods so freely as A. proteus. It grows to a much larger 

 s i ze (iiiri nc h) than, that species ; but, as in that so in this, the end of the individual is a quiet 

 rounding up and a sudden bursting, with the outcome of innumerable spherules or germinal spores. 



X. There is a closely related form, but larger, and even less inclined to exsert pseudopods, 

 using its villose end in moving like the tail-sucker of the leech. On account of its peculiarities, 

 Dr. Leidy refers it to Greeff s Pelomyxa.^ 



XI. An Amoeban animal with permanent bundles of long cylindrical tubular filaments trailing 

 from its hinder portion has the appropriate name of Ouramceba.^ 



XII. Deinamceba is a name given by Leidy to a curious villose Amoeban animalcule, about 

 0-2 millim. in diameter, which has the peculiarities (1) of having the body and the pseudopods some- 

 times papillose, sometimes bristling with minute, stiff, pointed filaments ; (2) of having at times an 

 enveloping layer of delicate, transparent, jelly-sarcode, itself covered with similar needle-like 

 filaments ; (3) of extreme variability of form, chiefly round, ovoid, and sub-cylindrical. " Indeed, 



" Proteus, the changeable sea-god. f Greek, pelos, mud ; myxa, mucus. J Greek, oura, a tail ; amoeba. 



Greek, dcinos, terrible ; amoeba. 



