THE SARCODINA 255 



sinks to a considerable depth. The swarm-spores are liberated by 

 the breaking-up of the central capsule. The subsequent develop- 

 ment of the swarm-spores when set free has not been made out. 



While the main features of the reproductive process are as stated above, 

 the cytological details of the formation of the swarm-spores is still a matter 

 of dispute. The subject is dealt with in the recent memoirs of Moroff on the 

 one part, and Hartmann and Hammer, Hartmann (60), and Huth, on the 

 other. The formation of the anisospores is generally regarded as a breaking- 

 up of the primary nucleus into chromidia, from a part of which the secondary 

 nuclei arise, which become those of the swarm-spores (compare Foraminifera). 

 But according to Hartmann and his adherents, the huge primary nuclei seen 

 in many Radiolaria are polyenergid nuclei or polykarya (p. 121) containing 

 a vast number of nuclear energids or monokarya, consisting each of chromatin, 

 in the form of a twisted thread or so-called " chromosome," and a centriole. 

 In the gamete-formation a great number of such monokarya are set free 

 from the primary nucleus to become the gamete-nuclei ; hence the so-called 

 " generative chromidia " set free from the nucleus are interpreted as secondary 

 nuclei or monokarya already formed within the primary nucleus. A similar 

 interpretation is given to the mitosis seen in the process of binary fission ; 

 the huge mitotic figure, composed of more than a thousand chromosomes, 

 is interpreted as being in reality made up of as many mitotic figures as there 

 are chromosomes, since each so-called " chromosome " is regarded as a single 



A B 



c 



FIG. 108. Swarm-spores of Collozoum inerme. A, Crystal- bearing swarm-spores, 

 agametes ; B, C, swarm-spores without crystals, gametes ; B, microspores 

 (microgametes) ; C, macrospores (macrogametes). After Hertwig. 



nuclear energid or monokaryon with its own centriole, the whole number of 

 energids dividing independently but synchronously to form the supposed 

 mitotic figure. 



According to Moroff and Stiasny, in Acanthometra pellucida a process of 

 multiplication is proceeding continually within the central capsule, until it 

 is entirely filled up with cells, from which the swarm-spores arise. In this 

 multiplication, termed by the authors " schizogony," trophic nuclei (" macro- 

 nuclei") and generative nuclei (" micronuclei ") are formed. The trophic 

 nuclei are the " yellow cells," which ultimately degenerate. Hence the Acan- 

 tharia are considered not to be single individuals, but colonies of animals which 

 have the extracapsular protoplasm, pseudopodia and skeleton in common. 



Finally, attention must be drawn to the peculiar organisms found in certain 

 Radiolaria, and regarded by some authorities as parasitic Flagellata (Silico- 

 flagellata, Borgert), by others as developmental stages, of the Radiolaria 

 themselves. See Delage and Herouard (6, p. 371). 



The Radiolaria are classified as follows : 



SUBORDER I. : PERIPYLARIA SEU SPUMELLARIA. Central capsule spherical, 

 perforated by evenly-distributed pores. Extracapsular region well developed. 

 Skeleton wanting or consisting of scattered spicules or of lattice-work shells, 

 developed in the extracapsular region, siliceous. 



Legion 1 : Collodaria. Skeleton wanting or simple in structure ; monozoic 

 forms. Five families. Examples : Thalassicolla (Fig. 13), Thalassophysa. 



Legion 2 : Sphcerellaria. Skeleton complex, usually with lattice-work 

 shell ; monozoic, generally small. Four families. 



