48 DUBLIN 



From among the botanists, however, has come very recently 

 convincing evidence in favor of the reducing division as a con- 

 stant factor in the formation of the germ cells. Gregoire and 

 Berghs, Farmer and Moore, Gregory, Lotsy,and, most important 

 of all, Strasburger, have, in a series of important works, all con- 

 cluded in favor of this division — many of the above having, in 

 the past, been the foremost advocates of the antagonistic view, 

 viz., that the two maturation divisions are both longitudinal or 

 equational. Typical of the rest is the work of Strasburger, 

 After a careful reexamination of his old material, Tradescantia. 

 etc., he has abandoned his old views and in a new form Galtonia 

 in which the conditions for study are exceptionally favorable, 

 describes processes from which the presence of a reducing di- 

 vision is unavoidable. The twelve chromosomes of the early 

 germ- cells unite into six double structures in the synapsis stage, 

 and these bending upon themselves and uniting at their free 

 ends become the rings of the first maturation. It is in this di- 

 vision that the univalent components are separated, the division 

 being thus transverse or reducing. The second maturation 

 mitosis then ensues and the chromosomes, as in the ordinary 

 somatic tissues, split longitudinally and pass to their respective 

 cells. There is thus, on the authority of a constantly increasmg 

 number of investigators, a condition of the germ-cells which, as 

 Sutton and Boveri have pointed out, alone can explain and give 

 basis for the very common and now almost universally recog- 

 nized Mendelian phenomena of heredity. 



E, Comparison of Oogenesis and Spermatogenesis. 



Finally, it is of considerable interest to find in Pedicellina the 

 complete similarity between the long series of processes in the 

 development of the germ-cells of both sexes. In the several 

 generations and nature of the oogonia and spermatogonia ; in 

 the presence of the V's ; in the last oogonial and spermato- 

 gonial telophase, with the subsequent reduction of the chromo- 

 somal number ; in the further history of the bivalent V's thus 

 formed ; their lengthening, irregular distribution within the nu- 

 cleus and the longitudinal splitting of their arms, the early male 



