and Reproductive Phenomena of the Amoeban Rhizopods. 449 



pseudopodia of Actinophrys — that these pseudopodia are for a 

 time rigid — that occasionally they are bent at an angle, and 

 again straightened — that sometimes, though rarely, they coalesce 

 with each other — that they are retractile into the parent mass — 

 that, within a period ranging from a few minutes to a few hours, 

 the whole of these pseudopodia may vanish and give place to 

 the lobose and polymorphous pseudopodia of Amoeba — and, 

 lastly, that the organism is stamped as a true Amoeba by the 

 presence of the villous appendage, the characters of the nucleus 

 and contractile vesicle, and the definite differentiation into an 

 anterior and posterior portion — I say, admitting the accuracy 

 of these facts, it is impossible to regard characters based on the 

 figure of the pseudopodia as of distinctive value either in the 

 case of species or of genera, in default of other and more im- 

 portant structural peculiarities. 



The following are the more detailed particulars of the transi- 

 tion in question. In the ' Annals ' for June last, a figure was 

 given of a specimen of Actinophrys under distention by a large 

 Pinnularia (see Annals, June, PI. X. fig. 4) — a remark being ap- 

 pended to the effect that it would be difficult to distinguish this 

 form from an Amoeba on the retraction of the pseudopodia. No 

 contractile vesicle was noted, but oil-globules were present 

 within the protoplasm of the diatom. Yov reasons to be given 

 hereafter, it is most probable that the figure is really that of an 

 Amoeba in the state preparatory to encystation, and that the 

 specinien was of a similar nature to the one figured in the plate 

 appended to this paper (PI. VIII. fig. 12), inasmuch as the pool 

 in which it occurred, like the pool in which my recent specimens 

 were found, was being rapidly dried up. 



But by far the most striking examples of Amoeba assuming 

 temporarily the external characters of Actinophrys were de- 

 tected recently. Whilst I write, they are still plentiful. They 

 are of small size, rarely exceeding in length ^-^th of an inch. 

 Before the transition from their normal state begins, they 

 exhibit every character of a small-sized but fully developed 

 specimen of Amoeba villosa — that is to say, a distinct villous 

 tuft, a spherical nucleus enclosed within a hyaline zone, one or 

 more active contractile vesicles, crystalloids, granules, and the 

 usual lobose pseudopodia of the species. But from one portion 

 of the surface we now see projected a group of short, tapeiing, 

 pointed pseudopodia, which rarely curve, but bend freely on 

 their axes like the spines of Echinus, although, of course, with- 

 out a vestige of special structure. In short, they closely re- 

 semble the short ciliary appendages of Ploesconia or Kerona, 

 without serving, as the latter do, for locomotion (Annals, April 

 1863, p. 390). 



