558 



Mr. J. E. S. Moore and Miss A. L. Embleton. [Dec. 5, 



premaiotic divisions is perfectly simple. In Triton each. Anlagen (or 

 prochromosome) becomes gradually enlarged and thickened into the long 

 premaiotic chromosomes of the spirem figure, while in Periplaneta they 

 gradually assume the form of dense short rods characteristic of the premaiotic 

 division figures of that arthropod. 



In both cases the chief interest of these bodies lies in the fact that they 

 obviously represent the chromosomes of division during rest ; and we may 

 say without reserve that their presence at all stages of rest between the 

 successive premaiotic divisions seems to conclusively prove the permanence of 

 the chromosomes from one cell generation to another. 



Examination of the resting maiotic nuclei given in figs. 1 and 2 shows 

 that, so far as can be seen, the Anlagen consist of irregular rods composed 

 chiefly of chromatin, and either suspended in a fine linin meshwork within 

 the nucleus or attached to the nuclear membrane, where the chromatin is seen 

 to be spread out, and to give to the membrane itself the peculiar thickened 

 appearance characteristic of the stage. No other structures with the exception 

 of irregular nucleoli are visible within the lasting premaiotic nuclei. 



Before the maiotic metamorphosis sets in the Anlagen are seen to be 

 single and discrete, figs. 2,3; but as we pass to an examination of the cells 

 in the later phases in the region c, where the synaptic change is gradually 

 proceeding towards the formation of the coarse spirem, we find that the 

 Anlagen are no longer single, in fact, the diminution in the number of what, 

 under a low power would be taken for nucleoli is seen to be produced by a 

 pairing of the bodies while the nuclei themselves still remain at rest. 



The appearance which such cells present is represented in figs. 1, 4, and 5. 

 Fig. 4 shows a cell in this condition in the same relative position as that 

 represented in fig. 2. The associations produced in this way (which we 

 propose to call gemini) are again represented in fig. 5. where the gemini 

 are seen end on, as were the single Anlagen in fig. 3. 



We have then in the testis of Triton premaiotic cells which, like the 

 premaiotic or somatic cells of rest of the animal's body, possess structures that 

 represent during rest the individual chromosomes of the successive division 

 figures, and these bodies during the first phase of the synaptic metamorphosis 

 that is perceptible, conjugate or pair so as to form 12 gemini in the place of 

 the 24 single Anlagen (prochromosomes). 



When the gemini have been produced it is seen, as in fig. 4, that they are 

 related in a conspicuous manner by shreds and strings of linin to chromatin 

 patches on the membrane of the nucleus ; and there are indications that before 

 the gemini are formed the linin of each single chromosome extends out to the 

 limits of the nucleus. 



