HELIOZOA 7 3 



in the plurinucleate marine genus Camptonema, each rod abuts 

 on a separate cap on the outer side of each nucleus. The 

 nucleus is single in all but the genera Actinosphaerium, 

 Myxastrum, Camptonema, and Gymnosphaera. The movements 

 of this group are very slow, and are not well understood. A 

 slow rolling over on the points of the rays has been noted, and 

 in Camptonema they move very decidedly to effect locomotion, 

 the whole body also moving Amoeba - fashion ; but of the 

 distinct movements of the species when floating no explanation 

 can be given. The richly vacuolate ectoplasm undoubtedly helps 

 to sustain the cell, and the extended rays must subserve the 

 same purpose by so widely extending the surface. Dimorpha 

 (Fig. 3 7, 5, p. 11 2) has the power of swimming by protruding a pair 

 of long flagella from the neighbourhood of the eccentric nucleus ; 

 and Myriophrys has an investment of long flagelliform cilia. 

 Actinomonas has a stalk and a single flagellum in addition to 

 the pseudopodia ; these genera form a transition to the Flagellata. 



Several species habitually contain green bodies, which multiply 

 by bipartition, and are probably Zoochlorellae, Chlamydomona- 

 didae of the same nature as we shall find in certain Ciliata (pp. 

 154, 158) in fresh-water Sponges (see p. 175), in Hydra viridis 

 (p. 256), and the marine Turbellarian Gonvoluta (Vol. II. p. 43). 



Eeproduction by fission is not rare, and in some cases {Acan- 

 thocystis) the cell becomes multinuclear, and buds off 1 -nucleate 

 cells. In such cases the buds at first lack a centrosome, and a 

 new one is formed first in the nucleus, and pas&es out into the 

 cytoplasm. These buds become 2-flagellate before settling down. 

 In Clathrulina the formation of 2-flagellate zoospores has long 

 been known (Fig. 20,3). In. Actinosphaerium (Ei^s.l^, 21), a. 

 large species, differing from Actinophrys only in the presence of 

 numerous nuclei in its endoplasm, a peculiar process, which we 

 have characterised as endogamy, results in the formation of resting 

 spores. The animal retracts its rays and encysts; and the 

 number of nuclei is much reduced by their mutual fusion, or by 

 the solution of many of them, or by a combination of the two 

 processes. The body then breaks up into cells with a single 

 nucleus, and each of these surrounds itself with a wall to form, a 

 cyst of the second order. Each of these divides, and the two ■ 

 sister cells then conjugate after the same fashion as in Actino- 

 phrys, but the nuclear divisions to form the coupling nucleus are 



