RECENT RESEARCnES ON THE RADIOLARIA. 



167 



and to regard their irregular sliape as due to incipient divisions, 

 preliminary to such break up. 



Thus, as to the whole process, it appears that 



(1) With regard to the colonies as wholes, they may perhaps 

 increase by spontaneous fission, or by giving off a single or a few 

 capsules. The existence of these modes of increase has not, how- 

 ever, been actually observed, though it is certain that single cap- 

 sules (however derived, whether from spores or from segmenta- 

 tion) do exist separately. The colonies may also be increased by 

 juxtaposition, and the mass of an existing colony by the rapid 

 fission of its component capsules, the process taking place centri- 

 fugally in the shelled and irregularly in the shelless forms. 



It is possible that new young capsules may range themselves 

 round old ones, so producing the above-described " extracapsular 

 bodies," which may, on the other hand, be a stage of spore-forma- 

 tion. 



(2) With regard to the capsules themselves, it is certain that they 

 may increase by spontaneous fission into two, three, or more secon- 

 dary capsules, and that this process may repeat itself indefinitely. 



(3) With regard to reproduction by spores, it is certain that such - 

 a process occurs in Acanthometra, Thalassicolla, SpJicerozoum, Col- 

 losphcera, and Collozoum, and most probably in all E-adiolarians. 



The spores are formed by the breaking up of the contents of the 

 central capsule into small particles, which become directly trans- 

 formed into the spores, each spore containing a nucleus and fat- 

 granules, and also a crystalline body when such bodies are found 

 within the capsules in which such spores arise. 



Each spore is provided, moreover, with a flagellum, and it is 

 doubtful whether more than one flagellum ever exists to one spore. 



The spores may be formed either by the breaking-up of the con- 

 tents of the capsule directly into them, or by its breaking up into 

 variously shaped masses of various sizes, which again break 

 up into such secondarily formed zoospores. In the latter case (as 

 far as yet observed) the primary cleavage results in the division 

 of the capsule-contents into two sets of masses, the masses of one 

 set being more subdivided than the masses of the other set, which 

 parts respectively give rise to two kinds of spores, microspores 

 and macrospores — bodies having, no doubt, diff*erent but as yet 

 unknown functions. 



It has been thought, as we have seen, that the same species may 

 have colonies of two kinds — one kind of colony breaking up into 

 spores of two kinds (both without crystals) ; the other kind of 



