608 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
cipitates of a fluid substance, as Held supposes. The author distin- 
guishes the strongly cbromatophilous microsomes (Tigroid), from the 
pale matricial substance in which these lie. 
As to the “fibrillar” appearance— seen, for instance, in the motor 
cells of the anterior cornu of the frog’s medulla, it is due not to a direct 
differentiation of the ground-substance of the plasma, but to the linear 
disposition of a finely granular material, probably the same as that 
which connects the tigroid masses. 
Lenhossek also notes that, in spite of much search, following his 
discovery of centrosomes and spheres in the spinal ganglion cells of the 
frog, he has been unable to discover these in the central nervous system 
of Mammals. 
Granular Leucocytes.* — Dr. G. L. Gulland has studied in a wide 
variety of cases the different kinds of leucocytes and their relations to 
one another. A few of his general results are the following : — Leuco- 
cytes whose finer structure is to be examined must be fixed by reagents, 
of which the best is sublimate ; drying is unreliable. It is impossible 
to distinguish a haemal and a ccelomic variety, for (1) lymphocytes are 
the precursors of all ; (2) leucocytes are not present in the blood in early 
foetal life ; (3) they are continually passing from blood to connective 
tissue and vice versa ; (4) their mitotic reproduction takes place almost 
entirely in adenoid tissue. 
Heidenhain’s observations on the relative positions of nucleus and 
centrosomes are correct. The “ organic radii ” are not entirely separate, 
but connected at every microsome by subsidiary threads. The nucleus 
does not lie free in the interfilar spaces, but its linin network is con- 
nected with the cytomitoma, and the two are perhaps to a certain extent 
interchangeable. 
The shape of the nucleus depends on ( 1) the relative sizes of cell- 
body and nucleus (Heidenhain’s law) ; (2) the position of the centro- 
somes ; (3) the condition of rest or movement of the cell. 
All varieties of leucocytes are merely stages in the development of a 
tissue. They may be divided for convenience, and with regard to the 
presence or absence of granules, into three main groups — the Hyaline, 
Acidophile, and Basophile. 
Red Blood-Corpuscles of Tadpoles.! — Dr. D. Giglio-Tos has studied 
the granulations or rather droplets seen in the red blood-corpuscles of 
the tadpoles of frogs and toads. Ranvier regarded them as vitelline 
granules, but they appear to consist of a special substance which the 
author calls u eritrocitina.” It is a refractive, somewhat viscous albumin- 
oid substance — soluble in absolute alcohol, acetic acid and caustic soda ; 
insoluble in chloroform or ammonia. The granulations or droplets are 
probably the same as those in the lamprey, which appear to arise from 
the nucleus, and to be associated with the formation of haemoglobin. 
Retina of Selachians.! — Herr L. Neumayer describes the minute 
structure of the ten layers of the retina in various Selachians. We note 
a few of his general conclusions. There is a general agreement between 
* Journ. Physiol., xix. (1896) pp. 385-417 (2 pis.). 
f Anat. Anzeig., xii. (1896) pp. 321-34. 
J Arch. f. Mikr. Anat., xlviii. (1896) pp. 83-111 (25 figs.). 
