Alcyonella. 



Z. ASCIDIOIDA. 

 Fig. 49. 



321 



/. 



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, g-rauules, spread in my«ads over the object-glass when the 

 perisperm is torn. The most minute observation has been employed 

 without success in fiiyjing 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 j^. 



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. 30.) This ar- 

 rangement becomes still more appa- 

 rent on boihng the ovum in alcohol, 

 Avhich 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 



