HELIOZOA. 1 ( J 



spore-formation sometimes takes place. This has been observed in 

 ActinospTicerium, in which form the spores acquire a silicious coat. 

 In some genera, e.</., Clathrulina the spores are hatched as flagellate* 

 forms. 



Conjugation of two or more individuals has been observed. Ac- 

 cording to Brauer the nuclei of Actinosphcerrium fuse with one 

 another, so that their number may be much reduced. Whether 

 this nuclear fusion takes place only in forms which have resulted 

 from conjugation, is not known. 



Schaudinn has recently published a preliminary account of the 

 encystment and conjugation of Actinophrys sol,] which is of special 

 interest in view of a similar process described by Wolters^ in the 

 Gregarines (Monocystis), and the division of nuclei preceding conju- 

 gation in the Ciliata. He finds that after two individuals have come 

 together and formed a cyst wall, the nucleus of each divides by 

 karyokinesis into two daughter nuclei, of which one is extruded 

 from the protoplasm, while the other unites with its fellow to 

 form the conjugation nucleus. The subsequent division of this 

 nucleus, together with the protoplasm, into two or four gives 

 rise to the resting cysts, from which after some days the young 

 Actinophrys escapes. The analogy of this process with the forma- 

 tion of the polar bodies in the maturing ova of higher animals is 

 striking. 



Order 1. Aphrothoraca. Heliozoa without a skeleton (sometimes temporarily 

 invested by a gelatinous membrane). Nudearia Cienk. body-form changeable, 

 multinucleate ; (Monobia, Vampyrclla, Myxastrum sometimes placed here). 

 Actinophrys Ehrb. (the sun animalcule) pseudopodia with axial fibre which 

 can be traced to the single central nucleus ; may form colonies by in- 

 complete fission. Actinosphcerium Stein, large, multinucleate ; Actinolophus 

 F. E. Sch. 



Order 2. Chlamydophora. Heliozoa with gelatinous envelope. Hctcrcphrys 

 Archer ; Sphcerastrum Greef. 



Order 3. Chalarothoraca. Heliozoa with skeleton of loosely arranged 

 isolated silicious spicules ; Pompholyxophrys Archer ; Saphidiophrys Archer ; 

 Pinacocystis H. and L. ; Pinaciophora Greef; Acanthocystis Carter. 



Order 4. Desmothoraca. Heliozoa with a stalked or unstalked shell per- 

 forated by numerous pores ; Clathrulina Cienk. ; Orbulinellci Entz. 



* Cienkowski, Arch. f. Mic. Anat., 1867, p. 311. 



t Fr. Schaudinn. " Uber die Copulation von Actinophrys sol." Sitzungsber. 

 d. K.pr. Akad. d. Wiss. zu Berlin, 1896, V. 



+ "Die conjugation und sporenbildung bei Gregarinen." Arch.f. Mikr. Anat. 

 XXXVII. p. 99. 



