374 THE MICROSCOPE. 



further organization. This substance is in the highest 

 degree extensible and contractile ; and from the main mass 

 are given out, now in one part and now in another, per- 

 fectly transparent rounded processes, which glide over the 

 glass like oil, and are then again merged in a central mass. 

 There is no external membrane. In the body of the 

 Amoeba there occur, besides the granules, clear spaces with 

 fluid contents, which are sometimes unchangeable in 

 form, and sometimes exhibit rhythmical contractions." 



Belonging to the family is the very curious Acineta of 

 Ehrenberg, Actinophrys sol, " sun-animalcule." This 

 creature consists of a jelly-like contractile substance, or 

 sarcode, with tentacular filaments radiating from the 

 central mass, in such a manner as to have suggested the 

 name for the species. It abounds in pools where Desmi- 

 diaceae are found in many parts around London ; they 

 are ravenous feeders, not only upon the Desmidiacece, but 

 also upon all kinds of minute spores and animalcules. 

 (Plate III. fig. 66.) It was on examining some beautiful 

 Desmidiacece that my attention was arrested by the 

 curious appearance of two or three very small Actinophrys 

 floating very lightly upon the surface of the w r ater, in the 

 form of a ball, with their delicate tentacular filaments 

 perfectly erect all over their bodies ; in fact, they seemed 

 to be floating upon these delicate filaments. 1 



The most beautiful forms of the Rhizopoda are found 

 among those possessing a calcareous covering, as the 

 Polythalamia, Rosalina, Faujasina, &c. ; their systematic 

 arrangement is founded upon their shells, which exhibit 

 a very great diversity in form. Out of these forms, it 

 would appear that the labours of various naturalists in the 

 last hundred years have made us acquainted with nearly 

 2,000 recent and fossil Foraminifera ; and although the 

 observations of Dr. Carpenter 2 tend to show the pro- 

 bability that very many of these supposed species are 

 merely varieties, still the number is sufficiently great 

 to prove the importance and interesting nature of the 

 inquiry. 



(1) Weston, Juurn. Micros. Science, vol. iv. New series, p. 110; Clapa- 

 rede, Ann. Nat. His. Second series, vol. xv. p. 211. 



(2) Carpenter's "Introduction to the Study of the Foraminifera," published 

 by the Ray Soc. 1S62. 



