106 THE RADIOLARIA 



zoidae both megaspores and microspores arise in the same individual ; 

 isospores in different individuals. Moreover, the asexual individuals 

 are not all alike, but in certain genera at least some produce extra- 

 capsular bodies (pp. 138-9), and those individuals which bud off these 

 structures are, according to Brandt, young forms. These fertile 

 young forms become in many cases heterosporous x/he extra- 

 capsular body forming the megaspores, the intracapsulum giving 

 rise to the microspores but in other cases the extracapsular bud 

 develops into a new central capsule. Consequently we have two 

 forms of heterosporous individuals and one isosporous form, and 

 Brandt suggests that there is an alternation between the hetero- 

 sporous and homosporous individuals. Famintzin, however, has 

 reinvestigated the matter, and finds, in the vast numbers of full- 

 grown colonies that occur in autumn at Naples, some are converted 

 into isospores, some into heterospores, and many have extracapsular 

 bodies. These last colonies divide into small winter ones, ' the 

 majority of which possess extracapsular buds and develop into 

 heterosporous forms. According to Famintzin there is no alter- 

 nation of generations (13). 



Whilst the Sphaerozoidae thus either become heterosporous 

 directly, or indirectly after division and the development of extra- 

 capsular bodies, the Collosphaeridae have no extracapsular buds, 

 and their mega- and microspores develop in separate individuals. 

 The skeleton when present takes the form of a perforated shell, 

 but notwithstanding these differences they are held to be rightly 

 separated from the Sphaerellaria, with which Haeckel formerly 

 united them. 



The Sphaerellaria include an immense number of solitary 

 chambered forms, the majority of which are spherical, the remainder 

 being elliptical or flattened. Radial bars unite the chambers, but 

 these bars are wholly ectoplasmic, and are never joined at the centre 

 of the endoplasm as in certain Acantharia. The nucleus remains- 

 single, but grows with the growth of the individual. 



The Acantharia form a primitive group of Radiolaria with many 

 interesting distinctive features. They retain homaxonic symmetry, 

 but the pores of the central capsule are less closely set than in the 

 Spumellaria. Through these pores there pass not only the cyto- 

 plasmic bridges between ectoplasm and endoplasm, but also two 

 other radiating structures, namely, stiff pseudopodia (axopodia) and 

 spicules. The latter meet in the centre of the capsule (Fig. 4 (7)), 

 the former surround the centre and alternate with the spicules 

 (Fig. 18), which pass outwards generally in five whorls. These 

 emerge from the ectoplasmic surface at points through which five 

 circles could be inscribed corresponding to the two tropical, two 

 polar, and equatorial lines of the globe. 



The whole disposition strongly suggests that the radiating 



