382 The Unity of the Organism 



It seems, therefore, entirely justifiable to extend the 

 application of Hacker's hypothesis of active developmental 

 centers for skeletal production in the extra-capsular sar- 

 code to organ production in the capsular membrane. 



In the absence of a systematic investigation of the devel- 

 opment of the adult Radiolarian from its swarm spores, we 

 have to be satisfied with such fragments of ontogenetic 

 knowledge of the group as students have had opportunity to 

 get. A few years ago Moroff and Stiasny studied at Triest 

 several developmental aspects of the well-known genus Acan- 

 thometron, figure 26. Besides their 'observations on the 

 complicated multiplication processes which take place in 

 the central capsule, involving both the chromatic and achro- 

 matic substances, and according to the authors, implicating 

 both macro- and micronuclci as well as merozoites, schizo- 

 zoites and swarm spores, the attention was also given to the 

 structure and to certain developmental phenomena of the 

 extra-capsular parts. 



The investigators were able to extend previous knowledge 

 of the adult extra-capsular parts. The extensions which 

 especially concern us pertain to the myophrisks m.y. 9 and 

 to the system of plasmic fibers (p.f-, figure 26) surrounding 

 the radiating spines (sp) of the skeleton. These fibers were 

 found to be much more numerous than previously described. 

 Some of them extend to the distal ends of the spines. "Around 

 each spine there is grouped a whole system of such fibers, 

 constituting the sheath of the spine, which in its form re- 

 sembles a tent." The individual fibers pass down into the 

 general extra-capsular mass where they anastomose with 

 others of the same tent and with those of the tents of other 

 spines. There are about twenty of these tents. The au- 

 thors believe these fibers to be not merely supporting, as 

 hitherto supposed, but pulling fibers. 



The myophrisks are distinct rod-like bodies arranged in 

 regular fashion around the spines some distance from the 



