1884.) Microscopy and Histology. 1179 
sectioned, Three cylinders, measuring 4, 6 and 9™ in diameter, 
will be found sufficient for all ordinary purposes, 
The apparatus above described can be adjusted to knives of 
different microtomes. It may be obtained from Gustav Stober in 
Wiirzburg. 
Tur Distomran Broop-sac or Sporocyst.—Our knowledge of 
the life-cycle of the digenic trematodes has become nearly com- 
plete through the researches of Leuckart, Thomas, Schauins- 
land and Biehringer. Schauinsland was the first to trace the de- 
velopment of the trematode embryo from the egg ; and Leuckart 
anarians, is shown by Biehringer to contain nuclei, and hence it 
must be regarded as a true epidermis, comparable with the Aypo- 
dermis of other worms. Hitherto the ciliated mantle of the em- 
bryo, which is thrown off during the transformation into a sporo- 
cyst, has been held to represent the entire ectoderm (epidermis), 
and hence the sporocyst was supposed to be without an ect er- 
mic layer. Biehringer takes a more rational view, holding that 
the ciliated mantle represents only the outer | 
rm, comparable to the outer epithelial layer of 
echinoderm or a nemertine. The so-called cuticula of the cer- 
carian larva is also shown to be not a cuticula butan epidermis. 
_2. Beneath the epidermis there is a thin muscular layer con- 
cared an outer stratum of transverse (circular) fibers and en 
inner stratum of longitudinal fibers. 
"ine The inner layer, which forms the chief part of the wall of 
€ sporocyst, may be called a germinal epithelium. ee 
_ Some sporocysts have a fourth layer enveloping the three 
a... ; but this layer, as was long e pointed 
rng orms no part of the proper W : : 
Tager has for the first time punting” the precise origin 
accessory membrane. Jt is formea from 
cles of the host, 
Origin of the Germ-cells of the Sporocyst—Th 
n of opinion between Leuckart and ot 
gin and nature of the cells which give rise " the yo 
mature sporocyst. The free-swimming disto! 
completely filled with coarsely granular cells, which are the 
1 . i i : i E en. Sem- 
A aE T 
