868 THE ANIMAL KINGDOM. 



often contains numerous orange particles in its ectosarc ; Chondropus 

 peculiar green spherules ; Acanthocystis flava reddish-yellow granules ; 

 PinacocysttS) &c. reddish-brown ; Pompholyxophrys exigua a single central 

 ruby-red globule. Chlorophyl bodies occur occasionally in Actinophrys 

 and sometimes in the endosarc of Actinosphaerium, constantly in the 

 ectosarc of Acanthocystis and Heterophrys myriapoda, in Sphaeratrum 

 Fockii, Raphidiophys viridis, and R. elegans. But colourless forms of 

 these species occur, and in this case colourless bodies, resembling 

 the chlorophyl bodies may be present 1 . Contractile vacuoles have 

 not been observed in Actinolophus, nor in all the species of some 

 skeletogenous genera, e. g. of Raphidiophrys. As to their number, Acti- 

 nophrys has one, Actinosphaeritun one to five ; but larger numbers are 

 sometimes found, e. g. twenty in Raphidiophrys pallida. They are either 

 deeply placed in the ectosarc, are not large, and do not bulge the surface, 

 or they are quite superficial, swell to a very great size, e. g. in Actinophrys 

 the vacuole may almost equal the body in diameter and project freely 

 above the surface. The new vacuole appears in the same place as the 

 old, and may originate from a remnant of it. Non-contractile vacuoles are 

 sometimes absent, sometimes sparingly present, in Actinolophus and most 

 skeletogenous genera. There are many in Actinophrys and Actinosphae- 

 rium, confined to the ectosarc in the former, in the latter small and 

 irregular in the endosarc, large, radially arranged, and close set in the 

 ectosarc. In both forms the largest are peripheral. A young Actino- 

 sphaerinm, however, has but a single radial layer. The ectosarcal vacuoles 

 disappear under mechanical and electrical stimuli. A nucleus has not 

 been observed in some of the little known forms. It is single in most 

 instances, but specimens occur with two or sometimes with several nuclei, 

 e. g. of Raphidiophrys pallida. Acanthocystis Italica has been only seen 

 with several nuclei ; Actinosphaerium, except in the youngest stage, is always 

 multinucleate ; a large example of it may contain 1-200 nuclei, and one, 

 0-85 mm. in size, is said by Carter to have had between 3-400. They 

 multiply by binary fission and with mitosis. The nucleus always lies in 

 the endosarc, centrally or excentrically as in Actinolophus, Acanthocystis, 



1 Are these bodies a part of the Heliozoon, or are they symbiotic Algae ? They multiply by 

 fission, but so do chlorophyl bodies (Greeff, A. M. A. xi. p. 12) ; they are very generally accompanied 

 by colourless bodies resembling them ; and' when they are absent, similar colourless bodies are as a 

 rule, if not always, present. The occasional expulsion of some of them in Acanthocystis viridis has 

 been witnessed by Greeff (A. M. A. v. p. 484) ; so, too, of certain yellow bodies in A. spinifera (Id. 

 op. cit. p. 494). Entz states that A. turfacea (viridis'} never ingests food (Biol. Centralblatt. ii. p. 

 463); that he has seen the chlorophyl bodies expelled from A.aculeata before encystation, their 

 subsequent multiplication, and rupture of the spinose skeleton (op. cit. p. 459). On the other hand, 

 Greeff has seen them in an encysted A. viridis (A. M. A. v. p. 489). Hertwig and Lesser observed 

 a colourless Acanthocystis turn green with chlorophyl bodies derived from digested algal spores 

 (A. M. A. x. suppl. p. 203). Leidy has figured a specimen containing bright red bodies, with a few 

 green (Freshwater Rhizopoda of N. America, PI. xliii. fig. 9). At present the question cannot be 

 regarded as decided. 



