20 Transactions of the Society. 



and over the delicate lining membranes through which aeration of 

 the blood may well take place. 



Before leaving the subject of the respiratory organs I will say 

 a word more as to my not adopting the view held by Nicolet and 

 Claparede, and generally received, that the two organs which look 

 like stigmata on the cephalothorax really are so. One hesitates 

 greatly to attack a conclusion supported by so much authority, but 

 Nicolet is really the only observer who has ever investigated 

 beyond the external appearance ; Claparede only dissected Hoplo- 

 ]}hora, and there he did not find anything in connection with the 

 so-called stigmata except the minute air-sacs referred to above. 

 The matter is one of fact ; of the tracheae large enough to be traced 

 I have not ever succeeded in finding one attached to the so-called 

 stigma, or proceeding from any air-sac attached to it, and I have 

 found them originating in other places, as detailed above. Again, 

 the pseudo- stigmata are quite as highly developed in the larvae 

 and nymphs as in the adults, although the tracheal system is quite 

 rudimentary in the immatm-e forms as far as the observations of 

 other arachnologists and of myself extend, a circumstance (as to the 

 absence of tracheas in immature forms) also observed by Pagen- 

 stecher in Ixodes and Tromhidium, and by Kramer in Gamasus, 

 Tarsonemiis, &c. ; and again the extremely small internal opening 

 of the pseudo-stigmata, which is almost or quite filled by the 

 peduncle of the so-called protecting hair (my pseudo-stigmatic 

 organ), is against the hypothesis of their being true stigmata. For 

 what it is worth, it may also be mentioned that in Pi/gmephorus 

 S]jinosus, a parasite of the mole, which possesses organs much 

 resembling the pseudo-stigmata of the Orihatidse, Dr. Kramer, its 

 discoverer, could not trace any tracheae to these organs ; * although 

 doubtless the weight of this is lessened by the fact that, in con- 

 sequence of want of specimens for investigation, he was not able to 

 trace the tracheae to any stigma. 



The Super-eoxal Glands. 



I have said above that Nicolet describes an air-sac which I can- 

 not find, but that I do find a sac, which I believe to be glandular, 

 not far from Nicolet's position, although not attached at the point 

 he names. This sac I propose to call the super-coxal gland, and I 

 have very little doubt, from Nicolet's drawing, that this is the 

 organ he saw and supposed to be connected with what he and 

 others imagined to be the stigma. When the dorsal exo-skeleton 

 of the cephalothorax, and the adipose tissue which underlies it, has 

 been removed, what appears to be the enlarged, blind end of a fine 



* " Zwei Parasitische Milbeu des Maulwurfs," Archiv f. Naturgesch., 43rd 

 year, Bd. 1, p. 257. 



