420 nil. £. KLEIN. 



embryo Triton the nuclei of all, or neiirly all, epithelial cells 

 undergo the indirect division ; but since it is equally pro- 

 bable that in the adult only a relatively small number of 

 nuclei possesses this property, it follows that many of them 

 lose this power and degenerate in the manner of division, 

 becoming degraded into nuclei that multiply after the more 

 plebeic manner of simple cleavage. By doing this, nature 

 evidently gains her end under great saving of energy, since 

 the existence of these nuclei is only of short duration. 



As supporting the assumption that nuclei divide after the 

 " direct " manner, viz. by cleavage, may be regarded those 

 nuclei in which the fibrils have arranged themselves, as if 

 those nuclei were going to divide in the indirect way, but 

 for some reason or other did not succeed in doing so, but 

 divided ultimately by cleavage. I refer to figs. 33, 34, and 

 35, which I have selected as the more characteristic forms ; 

 fig. 33 represents a " convolution," 34 and 35 " baskets " all 

 undergoing the " direct " mode of division. 



A good object for demonstrating the different forms of 

 nuclei while undergoing the indirect mode of division is 

 the bladder of adult frog prepared with chloride of gold. The 

 organ is filled iii situ with chloride of gold (^ per cent.) 

 until it is well distended ; it is then ligatured at the neck, 

 and placed in chloride of gold for about half an hour, 

 then opened and exposed to the light in slightly acidulated 

 water. Examining the inner surface of a small portion 

 spread out on a slide and mounted in glycerin, we meet 

 with many beautiful forms of " convolutions/^ " monasters," 

 " wreaths,^' " dyasters," and couples of small daughter 

 nuclei. The tail of tadpole prepared in chloride of gold 

 (see 'Handbook for the Physiolog. Laboratory,' p. 41) shows 

 also, amongst the epithelium of both surfaces, forms of 

 dividing nuclei, especially " baskets,^' " monasters," and 

 " dyasters." Their number, however, is relatively small. 

 The great majority of the nuclei present a uniform network 

 of fibrils or rods. The nuclei of the epithelium of the 

 bladder of frog are preferable to those of the tail of the tad- 

 pole, being of a much larger size. 



P. S. — Since the printing of the foregoing I have received 

 from my friend Professor Flemming, in Kiel, two of his 

 preparations of embryo Salamander, and I see in them the 

 most exquisite forms of nuclei dividing after the indirect 

 mode, as figured by F. in his paper. 



