OF THE PROTOZOA. ACTINOPHRYINA. 243 



Prof. Williamson and Dr. Carpenter, to which we would particularly refer 

 the inquirer intent on following out his knowledge of the Foraminifera, but 

 which both the dimensions and the character of the present work forbid the 

 attempt to condense or analyse in its pages. Prof. "Williamson's work, ' On the 

 Recent Foraminifera of Great Britain/ forms the volume for 1857, published 

 by the Ray Society. Dr. Carpenter's learned essays on the structure of 

 shells, on the value of form and other external characters in generic and spe- 

 cific groupings, and on the structural and physiological relations of several 

 genera, are to be found in the ' Transactions ' and in the ' Proceedings ' of 

 the Royal Society. 



Additional facts concerning both the structure and relations of the several 

 groups of Rhizopoda will be found in our Systematic History of them in Part II. 



SUBFAMILY OF RHIZOPODA, ACTINOPHRYINA. 

 (Plate XXIII. 24-37.) 



This is a remarkable group of Protozoa, which can take its place neither 

 with Ciliata nor strictly with Rhizopoda, although its affinities with the latter 

 are very close. Ehrenberg attached the several forms of this family with 

 which he was acquainted to his heterogeneous collection — the famil^^ Enchelia, 

 and referred them to five genera, viz. Actinophrys, TricJiodiseus, Podophrya, 

 Dendrosoma, and Acineta. Moreover, according to liis fundamental hypothesis, 

 he represented them to have a mouth and an anus, an alimentary canal with 

 ofi'shoots in the shape of stomach-vesicles, a sexual gland, and ova. Since 

 the Berlin professor's investigation of these animalcules was made, several 

 distinguished natm^alists have most carefully studied them, and particularly 

 the Actinophrys Sol. 



In oui' last edition we named a genus Alderia, in honour of Prof. Alder, to 

 distinguish certain organisms described by him in the Annals of Natural His- 

 tory (1851, vii. p. 427). Subsequently, however, that eminent natui^alist wrote 

 us to state that the name proposed had been abeady applied to a genus in an- 

 other class of animals ; and on fiu-ther consideration and reference to Stein's 

 researches, we were inclined to renounce their claim to a generic independ- 

 ence, and to consider them three forms of Podophrya. Dr. S. Wright has, 

 however, apparently observed the same beings very lately, and instituted a 

 new genus, EpJielota, to receive them {Edinb. New Phil. Journ. 1858, p. 6). 



Notwithstanding the very close affinities of Actinophryma and Acinetina, 

 there are sufficient differences between the two, and so many peculiar forms of 

 the latter that they deserve a particular consideration. 



The history of the first family is very fairly represented by that of Actino- 

 phrys Sol, or of Act. Eichornii, both of which have been very completely 

 studied by Siebold, KoUiker, Claparede, Stein, and Weston. Some diversity 

 prevails among these several observers respecting a few points in their organ- 

 ization, which it wiU be incumbent on us to notice in the proper place. The 

 species of Actinophrys have a circular figure, and are either spherical or so 

 compressed as to have a discoid form (XXIII. 28, 29). The distinctive 

 peuliarity of their figure is, however, due to the filaments or tentacles, which 

 radiate from aU parts of their surface and give the beings (to employ a 

 familiar and not inapt illustration) the appearance of a ball of cotton stuck 

 thickly over with pins ; for the filaments have nodular extremities, or, in 

 technical phrase, are capitate. The figure is determinate, and in this respect 

 contrasts with the protean changes of form exhibited by Rhizopoda. Not 

 that the figure is completely unalterable ; for slight variations are possible. 



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