344 Transactions of the Society. 



though with the exception of a very few, notably BoUes Lee and 

 Bonnevie, investigators of animal forms, have not directed attention 

 to it : its revelance to the interpretation of synapsis in animals I 

 have pointed out in a previous paper. 



The estimation of the metaphase complex is rendered difficult 

 by the fact that the heteromorphic elements are closely packed 

 and to some extent always superimposed, so that mitoses in which 

 each individual chromosome is completely separate from its neigh- 

 bours, and any chance of confusing V-shaped elements with rods 

 that are contiguous at one extremity only is eliminated, are ex- 

 tremely rare. A more striking case of the differentiation of a 

 diploid complex into pairs of different sizes and shapes could 

 hardly be cited : not two pairs of chromosomes are precisely the 

 same size, and with respect to shape at least five distinct types are 

 recofjnizable. Of these three pairs may be stated to display sub- 

 terminal attachment to the fibres of the achromatic spindle ; two 

 of them are most conveniently described as J's, the other having 

 the form of a square root sign. The latter are well seen in text- 

 figs, 1 and 3. Of the remainder, which appear to 1)e uniformly 

 symmetrical, one pair is similar in shape to a horseshoe, and the 

 remainder, probably niue pairs, are straight or bent rods and 

 small arcs. 



In most equatorial plates a varying number of minute granules 

 is seen, usually in the centre ; these are comparable to the cloud 

 of particles seen in the polar metaphase of the- oocytes of Phragma- 

 tobia by Seller. According to Seller they are chromatinic. I have 

 not had the opportunity of testing their reactions in the Tuatara, 

 since in differentiating nucleolar (plasmosome) material from 

 chromatin by such methods as that of Auerbach, previous treat- 

 ment with acetic acid must be avoided ; consequently I am not in 

 a position to be dogmatic as to the nature of these granules. But 

 I may at the same time add that I am not satisfied with the 

 evidence for Seller's interpretation.* They occur prolifically in 

 the heterotype mitosis of Hatteria, and are found clustered round 

 the polar ends of the spindle, as indicated in text-fig. 14. On the 

 whole they are reminiscent of the persistent remnants of the 

 plasmosome in Lihellula and Pcriplancta ; and in this connexion it 

 may be remarked that Jordan refers to the formation of chromidia 

 in the Chelonian genera. Owing to the confusion arising especially 

 from the binuclearity hypothesis, it has been of late the fashion to 

 disregard the existence of nuclear emissions, as Beckwith, and in 

 earlier work, Gattnby, have done; but the work of Dendy, Buchner, 



* Shortly before his death the late Prof. Doncaster wrote to me stating that 

 on reinvestigation of similar granules to those of Seller in Abraxas, he was con- 

 vinced that they were not chromatinic. Since he was unhappily prevented from 

 publishing any results under this heading, as one of his pupils I take the oppor- 

 tunity of adding this footnote. 



