Alcyonella. 
Z. ASCIDIOIDA. 
321 
Fig. 49. 
lular tissue of the same substance as the parietes ; and that the shield 
incloses, under a shell of the same nature as the rim, a glutinous cel- 
lular tissue, the cells of which are filled with transparent, apparently 
amylaceous, granules, spread in myriads over the object-glass when the 
perisperm is torn. The most minute observation has been employed 
without success in finding any indication of an organ analogous to 
the embryo. 
By a section parallel to the two faces the difference which exists 
between the structure of the rim and shield is made apparent. Of 
the former the coat, deprived of the tissue which it contains, is 
seen to be transparent and divided into 
cellules arranged in rays which point 
towards the centre of the organ ; while 
the resinous and woody thickness of 
the shield presents a great number of 
small globular yellowish cells dispos- 
ed in quincunx. (Fig. 50.) This ar- 
rangement becomes still more appa- 
rent on boiling the ovum in alcohol, 
which however, no otherwise than 
ether, does not seem to discolour it 
much. Its brown colour is not owing 
to the presence of iron, for a long soak- 
ing of the eggs in prussiate of potass 
sharpened with sulphuric acid has not 
communicated the slightest tint of 
blue to their surface, even when they 
have been bruised previous to the maceration. Alcohol changes to 
a golden yellow the original brown colour of the shield. Iodine 
x 
