LATTICE WORKERS, OR POLYCYSTINA. 97 



capsule, but in some groups there is a different pro- 

 cess introduced by the simple division of the unicel- 

 lular organism. This spontaneous division is common 

 in the social Radiolaria, and produces their colonies. 

 In, these cases the increase by division is nothing 

 else than an ordinary case of cell-division, in which 

 bisection of the nucleus precedes that of the cen- 

 tral capsule. Another mode of growth in the 

 colonies is the multiplication of the central capsules 

 by gemmation. The gemmules or capsular buds 

 are developed on the surface of the young central 

 capsules before they have secreted a membrane. 

 "They grow, usually in considerable numbers, from 

 the surface of the central capsule, which is sometimes 

 quite covered with them. Each bud usually contains 

 a raspberry-like bunch of shining fatty globules, and, 

 by means of reagents, a few larger, or a considerable 

 number of smaller; nuclei may be recognised in them. 

 The naked protoplasmic body of the bud is not 

 enclosed by any membrane. As soon as the buds 

 have reached a certain size, they are constricted off 

 from the central capsule, and separated from it. 

 Afterwards each bud becomes developed into a com- 

 plete central capsule, by surrounding itself with a 

 membrane, when it has attained a definite size. 



A peculiar method of reproduction, which has been 

 characterised .as an " alternation of generations," 

 occurs in the social Radiolaria, distinguished by the 



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