296 
Morphologie, Befruchtung, Teratologie, Cytologie. 
comes under this head. In 1896 Gallardo, by using an electrostatic 
field and obtaining therein “chains” of sulphate of quinine suspended 
in turpentine, produced a model representing the cell field in three 
dimensions instead of two only as in the magnetic models of dust 
on rough surfaces previously utilised. Gallardo’s view is much 
strengthened if we add to it the conception of the relative permea- 
bility of different substances, and the recognition of material “chains 
of force”, due to redistribution of substances of unequal permeability. 
The physicist generally treats of unlimited fields of force, but if 
the field is enclosed in a mask of highly permeable substance, the 
effect is to modify the arrangement of the “chains of force” until it 
closely recalls that of the spindle fibres. This leads us to suppose 
that the cytoplasmic “Hautschicht” is highly permeable. If we take 
an ordinary magnetic spindle and interpose midway a piece of 
charcoal iron, the chains of force will converge on to it just as the 
spindle fibres do on to a centrosome. We are thus led to assign a 
secondary röle to the centrosomes; they can no longer be regarded 
as the originators of the forces of the field, but are merely sources 
of supply of highly permeable material to hold and to convey the 
strain. The real difficulty of explaining mitosis as the result of a 
bipolar mitokinetic force is that we should expect the two poles to 
draw together, whereas in the cell the poles diverge. The Separation 
of the centrosomes is referred to two factors, 1) the turgescence of 
the cavity through which the spindle fibres run, 2) the pull of the 
outer cytoplasm which draws the centrosomes towards the outside 
of the cell. A. Robertson. 
Havet, T., Formation of the true nucleoli or plasmosomes 
of the somatic cells: A contribution to the study of the for- 
mation of the plasmosomes in the nerve and blood cells 
of some Batrachians, viz., Rana temporaria and Alytes obste- 
tricans. (Rep. Brit. Assoc. York (1906). p. 757. 1907.) 
Observations were made on nerve, blood, and connective tissue 
cells of tadpoles. The nucleolus of somatic cells has a central part 
staining with acid dyes and consisting of nuclear enchylema, while 
the peripheral part, which stains with basic dyes, is derived from 
chromosome material. The chromosomes in the telophase are radially 
arranged round the central part of the nucleolus and their internal 
extremities do not become vacuolated but persist as a granulär zone 
forming the periphery of the nucleolus. A. Robertson. 
Johnson, D. S., A new type of embryo sac in Peperomia. (Johns 
Hopkins Univ. Circular 195. p. 1—3. 1907.) 
This preliminary note describes the embryo sac of Peperomia 
hispidula , a species in which sixteen nuclei are formed as in P. 
pellucida, but in which as many as fourteen nuclei fuse to form the 
endosperm nucleus, while the other two nuclei belong to the egg 
and synergid respectively. It is inferred that there is less ground 
than before for the view that the endosperm is a sexually formed 
embryo. M. A. Chrysler. 
Kildahl, N. J., Development of the Walls in the Proembryo 
of Pinus Laricio. (Botanical Gazette XLIV. 1907. p. 102—107, 
Plates 8—9.) 
This short paper is based upon a very complete series of mitoses 
in the proembryo of Pinus Laricio . 
