EECEKT EESEAKCHES ON THE RADIOLARIA. 145 



Scattered round the capsule, they, in the complex forms, often 

 wander some distance into the circumcapsular gelatinous mass. 



Hertwig * deems it probable that they arise from nuclei which 

 pass out from within the capsule ; but there is no evidence for 

 this ; and Cienkowskif having found them vigorously multiplying 

 in dead Eadiolaria, suspects that they may be parasitic organisms. 

 This latter view is opposed by Hertwig on account of the great con- 

 stancy of their presence in almost all Eadiolaria. But undoubted 

 parasites are present with remarkable constancy in many higher 

 animals, while several diiRculties disappear if we may regard them 

 as parasites. It would, first, account for no other satisfactory ex- 

 planation of their origin having been arrived at ; secondly, for their 

 greatly varying number ; thirdly, for their survival and increase 

 amidst the decomposition of the individuals in which they live ; 

 and, lastly, it would explain the anomaly of their existence in such 

 creatures as Eadiolaria— i. e., the anomaly of unicellular animals 

 containing true cells within them. For the yellow cells are un- 

 doubted cells multiplying by spontaneous division of their cell- 

 contents, ear^h division surrounding itself by its own cell-wall 

 before the dissolution of the mother cell. Their size varies from 

 about O'OOS millim. to about 0"025 millim. 



Certain yet other extracapsular bodies have been noticed by 

 Hertwig X in Collozotion inerme surrounding the central capsules, 

 but also wandering far from them into the gelatinous investment. 

 They are mostly spheroidal, and from 0*02 millim. to 0°04 millim. 

 in diameter, though they may be more elongated. Each contains 

 small fat -particles, and osmic acid brings also into view some large 

 nuclei. The nature of these bodies is problematical ; but it is 

 not impossible that they may be new central capsules in an inci- 

 pient stage of existence. They may, however, be stages of the 

 reproductive process, in considering which they will be again re- 

 ferred to. 



* ' Histologie,' p. 19. 



t Archiy fiir mikrosk. Anat. 1871, Tol. vii. He also tells us that yellow- 

 coloured specks, which might be taken for young yellow cells, were due to the 

 Eadiolarian observed having fed on yellow Tintinnoids. 



\ L. c. p. 37. He considers that Haeckel's " estracapsulai-en Oelkugeln " 

 (p. 149, pi. XXV. fig. 13) may be the same bodies (though they are less regular 

 in form and more numerous than Haeckel's), as also MuUer's " sehr kleine 

 Nester " (Abhandl. Berlin, 1858, p. 5) and Cienkowski's " zusammengedrangte 

 Blasehen" (Archiv f. mikrosk. Anat. vol. Tii. 1871, p. 378, pi. xxix. fig. 29), 

 which looked quite like young capsules. 



