268 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
centre (fig. 12), and finally a double spiral filling the whole spaoe may 
result (fig. 13). 
Another effect of heat is the production of local rotations about 
horizontal axes. A portion of the marginal nucleus may thus be drawn 
into the interior of the drop (fig. 14) ; a fresh nucleus then forms on the 
edge, and may follow the first, and so on until the whole surface becomes 
covered with parallel nuclei (fig. 15). 
When a flattened-out drop is very strongly heated, it is gradually 
dissolved, and, in consequence of the above movements, the thickness 
diminishes most quickly at the centre. Accordingly a hole is soon 
formed, and the drop is changed into a ring. At the moment of pro- 
duction of the hole, one or two nuclei form on its edge. The same 
thing happens when there is an air-bubble in the interior of the mass 
(fig. 16). For this case the structure lines are represented in fig. 17. 
They correspond exactly to the electric lines of force in a dielectric, into 
which an insulated conducting sphere is brought. Effects similar to 
those produced by heat can be brought about by mechanical means. 
Fig. 18 represents the effect of the passage of an air-bubble into a large 
mass, by which the nuclei are drawn out into parallel threads, like the 
“ oligen Streifen ” observed with cholesteryl benzoate. 
Division of crystal drops. — When an ordinary liquid crystal is cut 
into two parts, each part forms a new individual with spherical form and 
nucleus like the original. Fig. 19 a, b , c, shows the division of a crystal 
by means of an air-bubble ; the crystal is first deformed, and then cut 
into two parts. 
Copulation of crystal drops. — In the case of two drops with central 
nuclei the union of two into one may take place in two ways, either by the 
two nuclei closing up to the double nucleus in the centre of the com- 
pound drop, or by one nucleus being driven off to the edge, while the 
one-half of the compound drop grows at the expense of the other. The 
first process is represented in figs. 20 a, b, c, to 23 a, b , c. One of the 
processes by which two drops with marginal nuclei may unite is 
explained by figs. 24 a, b, c, 25 a, b, c, and 26 a, b, c. The ultimate 
form taken by the complete union of two drops need not be the only 
possible stable one. Quite stable intermediate forms may occur, 
especially where several drops are united. Figs. 27, 28, and 29 show 
some examples of the copulation of drops with central nuclei. 
With regard to the copulation of dissimilar crystals, it was found 
that any one of the three organic substances could unite with any other. 
Their properties, however, were so similar that no striking result was 
obtained. 
In support of the contention that optically isotropic liquids should 
be considered as liquid crystals belonging to the regular system, the 
author brings forward the following considerations. In the conversion 
of a substance into an allotropic modification the newly formed crystals 
generally occur regularly orientated with respect to the earlier ones. 
Now suppose that in a fused mass of regular crystals this orientating effect 
acts upon the crystallized modification resulting from solidification, and 
the latter upon the liquid crystals formed by the fusion. Then by 
repeated fusion and solidification the visible solid crystals, as well as 
the invisible liquid ones, should always occupy the same positions, 
