46 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
possessed of apparently rudimentary nuclei, and that, further, a similar 
iron-containing substance obtains in the cytoplasm of ferment-forming 
cells. This substance, to which cytologists apply the term chromatin, 
cannot on theoretical grounds be regarded as constant in its molecular 
structure, even in the same organism. It is difficult to say whether 
there is anything different in the way in which the iron is held in the 
animal cell from that obtaining in the vegetable organism. As a rule, 
it is easier to liberate the iron with ammonium hydrogen sulphide from 
vegetable than animal cells, from the fact that haemoglobin, which is 
found in a large number of animal forms, is present in no vegetable 
organism. It seems probable that the iron is combined in animal chro- 
matin in a way unlike that in which it is held in the vegetable cell. 
The conditions known as anaemia and chlorosis in higher Vertebrates 
have been hitherto explained as caused by a diminished production of 
haemoglobin directly from organic or inorganic compounds absorbed 
by the intestine from food. They must now, however, be referred to a 
deficient supply of the primary iron-containing compound chromatin, 
not only in the haematoblasts, but in all the cells of the body. If we 
accept this explanation of the nature of chlorosis it may be inferred that 
the condition is not limited to animal organisms in which haemoglobin 
is found, although its occurrence in others may be difficult to detect, 
because of the total absence of this pigment. From this point of view 
animal chlorosis is fundamentally similar to the chlorosis of the Vegetable 
Kingdom. 
Absorption and Physiological Import of Iron.* — Dr. B. Schneider 
has experimented with Clavellina Bissoana Sav., and proved (a) the 
rapid natural absorption of iron by the living animal, ( [b ) its occurrence 
in the walls of the alimentary tract, hepatopancreas, tunic-cells, &c., 
and (c) the importance of the nuclei as the special areas where the iron 
is stored. 
He has also shown the almost general occurrence of iron oxides in the 
respiratory tissues and organs of aquatic Invertebrates. In some organs, 
whose respiratory function has been doubtful, the iron test succeeds, 
e. g. in the lobed ciliated membrane at the end of the proboscis in 
Sipunculus nudus, in the spiral threads at the anal region of Sternaspis 
thalassemoides , in the skin of Phascolosoma , Cerebratulus, Aphrodite , &c. 
Mr. Thomson’s Presidential Address.j — Our valued co-editor, 
Mr. J. Arthur Thomson, has published his presidential address to the 
Scottish Microscopical Society. He took as his subject the present 
phase of the theory of evolution. He discusses the characteristics of the 
great schools, and points out the various ways in which the problems 
are approached. The great problems before the evolutionist are those 
of variation, of heredity, of selection, and of isolation. The president has 
obviously been greatly impressed with Mr. Bateson’s work, ‘ Materials 
for the Study of Variation,’ which he describes as an endeavour to get 
out of the speculative mire in which, to the physicist’s contempt, the 
biologist still flounders. It is pointed out that the evolutionists’ funda- 
mental question, and the least answerable, is, what causes variation? 
* MT, Zool. Stat. Neapel, xii. (1895) pp. 208-16 (1 pi.). 
f Proc. Scot. Micr. Soc., 1894-5 (1895) pp. 178-210. 
