ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
73 
The sarcosporidia of sheep ( Sarcocystis tenella ) and tho largo 
psorosperra-sacs are, according to the author, stages of one and the same 
species ; their structure is very much the same as in the other forms. 
In the youngest stage these may be seen in some places beneath the 
cuticular cells (sporoblast mother-cells) from which sporoblasts are 
produced by nuclear fission and simultaneous division of the plasma ; 
the latter are cells with homogeneous plasma and large nucleus. The 
cells derived from these mother-cells form ball-like aggregations, and 
from these are produced in their turn sickle-shaped bodies. In the 
medium-sized tubes, cell-division, ball-formation, and growth of the tube 
in the longitudinal direction of the muscle-fibres are continually taking 
place. As soon as the resistance of the sarcolemma is removed by the 
size of the parasite cell-division and sheath-formation take place at 
the periphery, that is to say, the sarcosporidium-tube becomes a psoro- 
sperm-sac. Why the sarcosporidia should attain a greater size in the 
muscles of the larynx, tongue, and oesophagus than elsewhere, as for 
example in the heart, is unknown. 
The author appends some remarks on tubes which he has observed 
in Rotatoria (Brachionus). Their development could be followed, but 
whether they were related to the Sporozoa or to the Chytridiaceae was 
uncertain. 
Psorosperms of Darier’s Disease.* — Dr. W. Petersen considers that 
there is no doubt that the “ corps ronds ” and “ grains ” met with in 
Darier’s disease, are not psorosperms, but that they are degeneration 
forms of the epidermic cells ; for between the forms in question and the 
epidermic cells there is every variety of transition forms. The cell- 
inclusion appearances are only rarely met with, and these are easily 
explicable on mechanical grounds. These appearances are not of con- 
stant occurrence in Darier’s disease, and the same or similar appearances 
are found in other cases of hyper- and para-keratosis, where their origin 
is still more clear. They contain at definite stages keratohyalin and 
eleidin, and no kind of preparation shows appearances resembling the 
developmental stages of known psorosperms. Inoculation and cultiva- 
tion experiments fail. 
From the foregoing it would appear that the author does not admit 
the usually accepted facts, and therefore his inferences differ altogether 
from those who see in these appearances evidence of a parasite. 
Centralbl. f. Bakteriol. u. Parasitenk., xiv. (1893) pp. 477-88 (1 pi.). 
