200 Mr J. M. Macfarlane on the- 



fore identical with those previously dwelt upon, and need 

 not further concern us. 



A few words now on the nucleus, as to its surface and 

 contents outside the nucleolus. Of recent years it has 

 been regarded by most as possessing a distinct covering, to 

 which the term nuclear membrane has been given. In 

 very young cells of Scilla, where the nucleus is densely 

 surrounded by protoplasm, it is difficult to make out a 

 double contoured bounding wall ; but as vacuolation goes 

 on, and the protoplasm gets stringy, in like degree does 

 this membrane make itself evident. In epidermal cells of 

 Scilla, stained with eosin, it is of a pale homogeneous 

 colour, and doubly refractive, contrasting well with tlie 

 stringy and granular nuclear substance. In a few cells of 

 Scilla treated with alcoholic solution of eosin I have seen 

 it quite detached from the nuclear substance, over the 

 greater part of its surface ; the nuclear substance had 

 apparently shrunk from it or the latter had swollen out. 

 In my observations on Sinrogyra an experiment will be 

 explained wdiereby the presence of this membrane can be 

 positively demonstrated in one plant at least. 



The stringy and granular aspect of the nucleus has 

 lately given rise to much discussion. Butschli, Schwalbe, 

 Hertwig, Eimer, Klein, Flemming, and others, have recently 

 insisted on there being in the animal cell a homogeneous 

 network of fibrils, traversing the nuclear substance, and 

 attached to the inner side of the nuclear membrane. In 

 the young state of Ornithogalum and S. hifolia one can 

 plainly discern little filaments on the inner surface of the 

 still thin imclear membrane, which have the same clear 

 homogeneous appearance as it. It is exceedingly difficult, 

 however, to trace the fibrils for any length, since they seem 

 to form a dense plexus. If, however, a piece of pretty old 

 epidermis in which the nuclei are large and well formed 

 be selected, and stained in solution of eosin, or, better still, 

 in a ;i per cent, solution of chromic acid, to which 1 part 

 in 2000 of heliocin is added, this, when submitted to a 

 Hartnack's No. 10 immersion, displays most beautifully a 

 dense reticulum of clear homogeneous fibres, stretching 

 inwards from the equally clear homogeneous nuclear mem- 

 brane. If, then, the piece of epidermis be subjected to 



