B. F. Kingsbury 129 



apices of the Vs (their middle points) are toward the centrosome (?), 

 and in each case the portion toward the pole of the cell becomes fused. 

 This is offered without comment as worth consideration, in the firm 

 conviction that the chromatin changes cannot be explained in them- 

 selves. 



Assuming that the chromosomes of the spermatocyte are bivalent (of 

 which, as said, there is not evidence in Desmognathus), then it is that 

 in the first mitosis one end of the united chromosomes fuses; in the 

 second, the opposite end, suggesting a polarity in the chromosomes 

 themselves, which, indeed, their bivalence itself might be interpreted 

 as indicating. 



Summary. 



1. The " contraction figures " in the nucleus of the growing spermato- 

 cyte do not occur constantly in Desmognathus. 



2. The chromosomes of the spermatocyte are twelve in number, and 

 in their growth are horseshoe-shaped with- the ends toward the idiozome 

 and centrosomes, suggesting a polarity of the cell at this stage. 



3. Synapsis was not observed in the formation of the chromosomes of 

 the spermatocyte. 



4. The first division of the spermatocyte is heterotypic, with ring- 

 formation by incomplete splitting. 



5. The second splitting of the chromosomes in the first division is 

 believed to be the precocious fission of the second division. 



6. The daughter-chromosomes of the second spermatocyte remain 

 fused together at their apices to form X's. 



7. Both divisions of the spermatocyte are believed to be equation 

 divisions, and no qualitative reduction takes place. 



8. The spindle in the second division is believed to be formed by the 

 fusion of two sets of radiations. 



9. The first and second divisions of the spermatocyte have certain 

 similarities and differences that are suggestive. A comparison with 

 other forms is given. 



10. The structure of the testis, spermatogenetic cycle, and the life 



cycle of the lobules are discussed. 



Histological Laboratory, Cornell University, 

 August 30, 1901. 



LITEEATUEE CITED. 



Atkinson, G. F., gg. — Studies on reduction in plants. I. Reducing division 

 in Arisaema triphyllum by ring and tetrad-formation during 

 sporogenesis. 11. Reducing division of the chromosomes in Tril- 

 lium grandiflorum during sporogenesis. Bot. Gazette, Vol. 

 XXVIII, pp. 1-26. 



