823 
crossing under angles of 90° will never manifest an optical rotation. 
The supposition made by Marrarp is, therefore, only allowable 
for pseudo-tetragonal crystals without optical rotation, and there is 
no possibility to explain the special behaviour of real pseudo-tetra- 
gonal crystals endowed with rotatory power in this way, at least 
in those cases, where the molecules of the crystallised substance 
do not possess a molecular rotation of their own. It will be necessary 
to look for a special explanation in all cases concerning this kind 
of objects, as e.g. in that of the pseudo-tetragonal ethylenediamine- 
sulphate, ete. 
§ 5. On closer examination of the original photographic plates 
of the patterns obtained with the hexagonal and octogonal complexes, 
which correspond with the projection-figures 2a and 3a, it became 
evident that, although the situation of the spots on the plates 
completely agreed with that of the normal images in fig. 2a and 38a, 
yet a distinct and rigorously determined abnormal distribution of 
their intensities was present, in such a way, that equivalent spots 
in the images did not possess the same intensity. Especially in the 
immediate vicinity of the centre, where very intensive spots were 
situated, the said phenomenon manifested itself most clearly. A more 
detailed study taught us, that this distribution of the intensities in 
the two images was, as drawn in the figures 25 and 35, i, e. 
symmetrical with respect to only a single plane. By special experiments 
it could be proved, that these anomalies did not depend on the 
position of the preparation with respect to the plane of the anti- 
cathode, or generally, to that of the luminous source: for on turning 
the preparation from its original position through 45° e.g., the plane 
of symmetry £ in the images appeared to have turned also through 
the same angle on the new photograms. The cause of the said 
abnormalities must, therefore, be ascribed to the preparations them- 
selves; and the close analogy of these anomalies with those formerly 
observed by us in real pseudo-symmetrical crystals, must be obvious, 
as also in those cases we observed a bilateral symmetry of the 
pattern, instead of the expected one, as was e.g. demonstrated with 
rac. triethylenediamine-cobalti-bromide and other preparations. The 
chief difference between these cases is, that in the preparations 
formerly studied, a number of spots were lacking altogether, their 
intensities being reduced to zero. Thus the bilateral symmetry of 
the patterns came there to expression in a higher degree, than was 
the case in our photograms which were obtained with objects, 
composed of a much smaller number of superimposed lamellae. 
