440 



EHIZOPODA RADIOLARIA '. ACTINOPHRYS. 



liquid. Although the existence of a ' nucleus ' in Actinophrys has 

 been denied, yet its presence (in certain species at least) must be 

 regarded as a well-established fact. It presents itself as a flat- 

 tened vesicular body with a well-defined margin, usually of cir- 

 cular outline, and very pellucid ; and its central portion is occu- 

 pied by an aggregation of granular particles, less defined at its 

 margin and less regular in shape. It may be brought into view 

 either by crushing the body of the animalcule, or by treating it 

 with dilute acetic acid. Throughout the body, but more particu- 

 larly near its surface, there are to be observed ' vacuoles ' occupied 

 by a watery fluid ; these have no definite boundary, and may easily 

 be artificially made either to coalesce into larger ones, or to sub- 

 divide into smaller ; sometimes they have such a regularity of 

 arrangement as to give to the intervening sarcode-substance the 



Fig. 233. 



Actinophrys sol, in different states:— a, in its ordinary sun-like 

 form, with a prominent Contractile Vesicle, o ; b, in the act of 

 division or of conjugation, with two Contractile Vesicles, o, o ; 

 c, in the act of feeding ; n, in the act of discharging faecal (?) 

 matters, a and b. 



appearance of a cellular structure. A Contractile Vesicle, pul- 

 sating rhythmically with considerable regularity, is always to be 

 distinguished either in the midst of the sarcode-body or (more 

 commonly) at or near its surface ; and it sometimes projects con- 

 siderably from this in the form of a flattened sacculus with a 



