128 BULLETIN OF THE 
have found less serviceable than the stains above mentioned. After 
staining, the preparations were dehydrated, cleared with oil of cloves, 
and mounted in benzole-balsam. 
The embryo is enveloped by three epithelial membranes, the ovarian 
capsule, the membrana serosa, and the amnion, —named in order from 
without inward. 
The serosa and amnion are strictly embryonic structures, analogous 
to the footal membranes of the higher Vertebrates. There are two 
contradictory accounts as to the manner of their formation. Possibly 
they do not arise in the same way in all genera of scorpions. In a 
brief communication by Kowalevsky und Schulgin (’86, p. 526) upon 
the development of Androctonus ornatus, it is stated that they originate 
as a fold from the edge of the blastoderm, the outer layer of the fold 
forming the serosa, the inner the amnion. The fold grows up over the 
blastoderm, the edges coalesce, and the membranes finally separate from 
the ovum. ‘The more recent account by Laurie (’90, p. 114) states that 
in Huscorpius the serosa arises by a proliferation of the peripheral cells 
of the blastoderm, extends as a delicate membrane forward and back- 
ward over the egg, which it finally covers completely, and then becomes 
entirely separate from the blastoderm. The formation of the amnion 
begins when the serosa has covered about two thirds of the embryo, and, 
like the serosa, its origin is ectodermic. The amnion, however, “ never 
loses its connection with the epiblast as the serous membrane has now 
done, but remains attached to its edges and only extends round the 
egg as the epiblast extends” (p. 116). Unfortunately, I have not 
obtained sufficiently early stages of Centrurus to ascertain how its mem- 
branes arise, but, in removing the latter from the embryo, I have never 
found the amnion attached to the ectoderm. The membrane which I 
” Tat first wrongly took to be the 
have called the “ovarian capsule 
follicular epithelium, and under this supposition it was indicated as e’th. 
fol. in Figure 2. Like the follicular epithelium, it arises from the 
ovarian tube; but the follicle is formed as a diverticulum of the tube, 
previous to the maturation of the ovum, and serves as a nutritive cap- 
sule for the latter during its growth. The ovarian capsule, on the 
contrary, is that part of the ovarian tube which receives the ovum after 
fertilization, and enlarges to accommodate the growth of the embryo. 
The feetal membranes fit so loosely over the embryo that they can be 
easily removed in a single piece. In late stages, the ovarian capsule is 
readily separable from the membranes ; in earlier stages, it adheres closely 
to them. It is rarely possible to separate the serosa from the amnion, 
