348 Transactio7is of the Society. 



traction in Anguis and Sphenodon as in Mammals (cf. de Wini- 

 warter and Federley) indicates that the Eeptiles should prove 

 specially favourable for the study of synapsis. That this process 

 of pairing actually constitutes syndesis or synapsis cannot be 

 strictly inferred, seeing that the actual numerical relations of the 

 loops were not actually estimated before and after the process ; 

 it can, however, be said that the whole course of events is entirely 

 characteristic of other forms where the correspondence of the 

 leptotene loops and telophase chromosomes has been established. 



Previous remarks on the genesis of the leptotene loops indicate 

 that for Hatteria, as in the case of Libellula, I regard the polarity 

 of the telophase as affording the key to the interpretation of the 

 "bouquet" figure (fig. 9). I am aware that some of the most 

 competent animal cytologists who have investigated the meiotic 

 phase, as, for example, de Winiwarter and Agar, describe a diffuse 

 and tangled leptotene stage before the bouquet arrangement is 

 manifest ; but, since the arrangement of the leptotene filaments is 

 often so intricate that only when seen in a plane parallel to the 

 axis of the bouquet can its character be recognized, and since 

 moreover the susceptibility of the leptotene filaments to defective 

 technique is notorious, the interpretation that I have given in the 

 case of Libellula merits a renewed attention to the orioin of the 

 bouquet loops. Dr. Euggles Gates has pointed out to me as an 

 objection to a telophasic interpretation of centrotaxis that the 

 position of the attraction sphere with reference to the convergence 

 of the loops is different in the two cases ; but Morse's observation 

 on the position of the centrioles in relation to the synaptic pro- 

 cesses of Blattids weaken this contention. Further light on this 

 point should be obtainable from the study of meiotic nuclei from 

 cells showing spindle remains such as are frequently found in the 

 ■ rosettes of oocytes in ovarioles of Hymen op tera. 



The approximation of the contracted filaments to form the 

 thickened reduced pachytene threads is soon followed by a loosening 

 of the bouquet figure, so that the still polarized chromatin loops 

 become once more contiguous with the nuclear membrane, and 

 now display the marked longitudinal fission which defines the 

 diplotene stage and leads up to the elaboration of the heterotype 

 chromosomes. The uniformity which prevails in the meiotic 

 phase of animals is specially emphasized at this point, for the 

 diplotene stage is one that is universally present ; and this, it 

 appears to me, constitutes a formidable, if not indeed an impregnable, 

 objection to the view that conjugation of homologous chromosomes 

 is effected in some species by lateral association and in other cases 

 by a terminal union. The validity of the parasynaptic interpreta- 

 tion originally put forward in 1900 by de Winiwarter as applied 

 to those forms which have provided pre-eminently favourable 

 material for investigation (Felis, Batrachoseps, Tomopteris, 



