1887 | Embryology. "20I 
G. 6. Portion of proboscis, showing the five series of smaller hooks in sg and 
a zie of the larger hooks at the side, a two hundred and twenty-five diam- ~ 
eters. 
i ae X Cyst with endocyst, from surface of liver of Cydium regale, enlarged six 
iame 
re 3. Endocyst renting i liberated from its cyst, slightly compressed and 
showing the coiled embryo T Scat mae at vee in the “head,” enlarged nine 
owe oe 
The same, subjected to greater pressure, Somn the embryo in the act of 
Piety “from the blas stocyst, enlarged nine dia 
Fic. 10. The same, with head freed from the ‘blastocyst, but still attached pos- 
teriorly to the “ head” of the blastocyst. The bothria are seen from below as they 
are spread out and applied to the under glass of. oh compressor, enlarged twenty- 
five eres eters. 
Outline of ra with its blastocyst now-attached like a rudimentary 
dohil; calang eds six diam 
ai Hiei near ai or proboscis, enlarged three hundred and fifty diam- 
a II å. Portion of proboscis, enlarged two aes bag and twenty-five diameters. 
All the figures drawn from life by Mrs. Edwin Lint 
Edwin Linton. 
ee of Scorpions.—Kowalevsky and Schulgin have 
a paper on the development of Androctonus ornatus in the 
pr S Centralblatt (vi. pp. 525- 532, 1886) which throws 
much light on these forms. As long as the egg remains in the 
ovarium it is not impregnated. Segmentation begins in the 
uterus. Their earliest embryo had the blastoderm completely 
formed at one pole of the egg, and at this time no nuclei were to 
be seen in the yolk. The first appearance of a differentiation 
into germ-layers was seen in the appearance of a swelling beneath 
blastoderm cells and sink to the lower layer. This germin 
area is circular in outline. The next step consists in the forma- 
tion of the embryonic envelopes, which arise as a circular Mpt 
cature ok the blastoderm in a manner analogous to thos 
Hexapods. Now the germinal area elongates, aod one af oe 
iceabalicy retains its breadth while the other (abdominal) becomes 
thicker and longer. During these processes many cells separate 
from the lower layer (ento-mesodermal) cells and sink into the 
olk. These cells are not regarded as forming any of sa tissue 
of the scorpion, but as digesting or softening the y e 
entoderm arises as a layer of cells which separate kon the ento- 
mesodermal layer and come to lie close upon the yolk. These 
rapidly spread over the yolk, which has already been enclosed 
by the amnion and serosa. The entoderm cells modify the outer 
layer of the yolk and then take up the modified deutoplasm, at 
the same time taking on the character of a cylindrical epithelium. 
The abdomen now grows out, and a portion of the mesenteron 
extends into it as far as the penultimate segment, where it unites 
with the proctodeum. The central portion of the mesenteron is 
latest in being differentiated io the tubular mid-gut and the 
