STIGMATIC OPEECULA IN THE SCORPION. 31 
Obvious as this fact is^ it has hitherto been almost en- 
tirely overlooked by naturalists who have directed their 
attention to the study of these interesting arachnids. The 
only person who seems to have had any knowledge of the 
fact that the stigmata can be opened and closed, is Emile 
Blanchard. He says " les stigmates se ferment et s'ouvrent 
plus ou moins ; ces mouvements sont executes par des 
muscles But serious doubts have been enter- 
tained as regards the accuracy of his observation. Felix 
Plateau, writing four-years back says "on a vu, plus haut, 
qu' Emile Blanchard parle de mouvements elfectues par les 
orifices stigmatiques. Ces mouvements sont, pour moi, 
tout ce qu'il y a de plus douteux. Non seulemeut je n'ai 
pas reussi a les constater mais Leon Dutour dont les etudes 
sur les Scorpions ont ete faites avec beaucoup de soin 
s'exprime ainsi ma plus forte loupe braquee des 
demi-heures entieres sur les stigmates de 1' animal vivant 
et fixe sur le dos, ne m^a jamais permis d'y saisir le moindre 
mouvemeut, malgre le soin d'y projeter de temps en temps 
un rayon de soleil. Mes lentilles, ma patience ont echoue a 
me rendre sensible ce jeu, ce mecanisme respiratoire. " ' 
Attached to the posterior wall of each stigma, is a plate 
covered with a thin layer of chitin, which may be called 
the " stigmatic operculum^' In the anterior portion of the 
operculum, which, when seen with the naked eye looks 
whiter than the rest, the chitin is thick and peculiarly 
modified. Viewed under the microscope it appears as a 
mass of polygonal bodies which look like the cells of a 
honey-comb. In section, it is seen to consist of Chitinoua 
rods, the free ends of which have somewhat the shape of 
inverted cups. These rods look like mushrooms with long 
stalks. When the stigma is open, this anterior portion of 
the operculum is not seen. When it is shut, only half of it 
' Archives Biologie, tome VII, page 339. 
