GERM CELLS IN PEDICELLIXA AMERICANA 47 



are distinctly like those described by all authors for the Am- 

 phibia. The second division is then longitudinal. 



After a careful examination of the evidence adduced in its 

 favor, I am convinced, in the light of the processes described in 

 Pedicellina, that the fundamental conception of Schockaert's is 

 full of difficulty. It is quite evident that the crux of the whole 

 question lies in the origin of the figures of the maturation divi- 

 sion. But as the author himself points out, there is no structural 

 continuity between the bivalvents of the early oocytes and the 

 longitudinally split rods which later conjugate. It is this hiatus 

 that throws uncertainty on the constitution of these latter 

 structures, and which makes positive interpretation of the later 

 stages quite impossible. What is more damaging, however, is 

 the fact that these structures are present in what appears to be 

 the reduced number. Should this be the case, the supposed 

 succeeding conjugation would still further reduce the chromo- 

 somes to one quarter the normal number, and the probability 

 of the process, for which very little evidence is given, would be 

 destroyed. 



Altogether, it seems far more probable, on the evidence pre- 

 sented, to consider the extended double rods of the late growth 

 period (Fig. 50, PL IV) not as the result of a post-synaptic 

 conjugation, as the author has done, but rather as persistent 

 structures from the earliest oocytes. The single rods would 

 then each correspond to one half of the loops of the synapsis 

 period. As in Pcripatus and Bracliystola, the pair of free ends 

 of the loops, I believe, come later into connection and thus 

 produce the rings and ellipses, and by the still further lateral 

 union the homogeneous "batonnets" of the maturation figure. 

 As in these Arthropod types, also, the early longitudinal split 

 in the loops has disappeared to reappear later in the anaphase 

 of the first maturation, division. The resulting structures are, 

 to be sure, of such a constitution as to insure the same result in 

 the first division as Schockaert concludes, but they are thus 

 derived through a series of processes in accordance with what 

 has been most clearly observed in other forms, but what is 

 more significant, in a manner in far better agreement with the 

 figures. 



