No. I.] SPERMATOGENESIS OF BATRACHOSEPS. d>J 



connected with the formation of the contractile fibers. The 

 centrosphere is globular or rounded while at rest ; when in 

 activity it is amoeboid and its nature appears to be that of an 

 organ of locomotion, by which the archosome and the accessory 

 archosomes can move from one place to another in the cell. 



VIII. The central-spindle fibers, the polar fibers, and the 

 mantle fibers do not penetrate the outer or centrosphere of the 

 archosome. The only fibers which penetrate this sphere are 

 the contractile fibers ; all others begin at the outer edge of the 

 centrosphere. The contractile fibers show from the beginning 

 a different structure, being strongly beaded. Their structure 

 greatly recalls that of a striated muscle cell. The fibers of the 

 fiber cones are formed for the purpose of pulling away the 

 cytoplasmic membrane from the nucleus, in order to allow this 

 latter body to pass through a stage of growth unhampered by 

 the surrounding cytoplasm. These fiber cones are presided 

 over by accessory archosomes. Another set of fibers, the 

 retractile fibers, is formed for the purpose of pulling the two 

 daughter-cells apart. This set seems to emanate partly from 

 the archosome, partly from the accessory archosomes. The 

 fibers of the central spindle and those of the fiber cones become 

 also beaded shortly before they dissolve. 



IX. The cell generations of the testes of Batrachoseps are as 

 follows : Polymorphous spermatogonia, auxocytes, spermato- 

 cytes, spermatids. They are characterized as follows : Poly- 

 morphous spermatogonia, a large polymorphous nucleus during 

 the resting stage, a perfect resting stage before mitosis ; during 

 that stage there are no chromomeres, no chromosomes, and 

 no leaders ; somatic mitosis with twenty-four chromosomes ; 

 there are three or four generations, but only the first pos- 

 sess polymorphous nucleus and the characteristics pertaining 

 to it. The auxocytes are characterized thus : an imperfect 

 resting stage before mitosis ; the formation of twelve bretzel- 

 shaped chromosomes which divide by heterotypic mitosis and by 

 an equation division ; a confluent umbrella stage of the chromo- 

 somes in which the chromoplasts and the chromosomes become 

 entirely confluent. The growth of the nucleus is accompanied 

 by the formation of a greater or lesser number of fiber cones. 



