88 RISEN. [Vol. XVII. 



The spermatocytes are characterized thus : the chromosomes 

 are thrown on the central spindle as split F's ; the central 

 spindle is often formed by the fusion of two opposite fiber 

 cones, in which case the accessory centrosomes assume the 

 functions of archosomes ; mitosis by the homoeotypic process 

 and by equation division ; the chromosomes are twelve in num- 

 ber ; only one generation. 



X. The mitosis of these genetic cells is the result of two 

 parallel independent processes, for which I propose the names 

 " radiosomic " and " chromosomic." The radiosomic process 

 has for its purpose the formation and evolution of the spindles 

 and fibers (necessary for the dissolution of the nuclear mem- 

 brane and for the separation and equation of the chromosomes) 

 and the reconstitution of the cytosome. The radiosomic process 

 is directed by the archosomes and the accessory archosomes. 

 The chromosomic process has for its object to form the leaders 

 through the arrangement and formation of chromomeres, the 

 arrangement of the chromioles into chromomeres, the contrac- 

 tion of the leaders into chromosomes, the splitting of the 

 leaders, and the separation of the split halves by the aid of 

 the linin and the linoplasts. The chromosomic process is con- 

 ducted by the chromoplasts. The cooperation of the two 

 processes commences possibly with the arrangement of the 

 leaders to form a bouquet, at which time the spheres appear to 

 attract the ends of the leaders. But the first time when the 

 two processes cooperate with a certainty is when the nuclear 

 membrane is dissolved by the mantle fibers. The cooperation 

 of the two processes has for object the equation division and 

 perfect separation of the chromosomes, and indirectly the divi- 

 sion of the chromioles. The archosomes and accessory archo- 

 somes take no part in the chromosomic process. 



XI. The perfect resting stage of the nucleus of the poly- 

 morphous spermatogonium belongs to a phylogenetically very 

 primitive type of nucleus. In this type the chromomeres and 

 chromosomes have not yet become a necessity, the chromioles 

 simply being suspended on chromoplasmic and linin threads. 



XII. The confluent umbrella stage of the nucleus is not an 

 artefact, but an actual stage in the development and growth of 



