16 Transactions of the Society. 



have an ovipositor, and as he found the organ he took it to be the 

 penis — a curious idea, for although that organ certainly attains a 

 great length in some of the Acarina, e. g. Proctojjhylodes (Derma- 

 Jeichus) gJandarinus Koch, yet a male organ longer than the 

 whole body, and thicker than the leg, would be an anomaly. 

 Having settled this to his own satisfaction, Dujardin declared the 

 opening below the hinder pair of plates to be the vulva, and concluded 

 that the Orihatidse were hermaphrodite; in this view Dujardin 

 entu'ely forgot that the animals required an anus, and these errors 

 still survive although Nicolet and Claparede have exposed them. 



Respiratory Organs. 



Nicolet* describes the respiratory system of the Oribatidm 

 as consisting of two conspicuous stigmata, one on each side of 

 the posterior portion of the cephalothorax, each stigma being 

 funnel-shaped, and opening, by a minute circular aperture, into 

 an air-sac placed transversely in the body and bent upon itself 

 in order to reach the stigma, and of four larger and two smaller 

 trachege on each side, the longer ones being distributed two 

 to the dorsal and two to the ventral surface, and forming many 

 convolutions, and the two smaller being allotted to the cephalo- 

 thorax ; and he states that this arrangement is general to_ all the 

 Orihatidse, and only varies in other families of Acarina. I 

 confess that until I began actually to dissect out the respiratory 

 organs I never for an instant doubted the entire correctness of this 

 description, and for a considerable time after my dissections had 

 commenced, I thought that I must have missed the arrangement 

 described by the French naturahst in consequence of the difficulty 

 of the investigation. I found, however, that I could not, in any 

 instance, trace the tracheae up to the position described, nor could 

 I find any air-sac in this place from which they originated, 

 although I found a sac or tube, apparently glandular, not far off, 

 but with liquid contents instead of air and not connected with the 

 tracheae. In the course of this investigation I have dissected over 

 fifty specimens belonging to numerous species : I find, with sincere 

 regret, that although many parts of Nicolet's descriptions are correct, 

 yet I am not able to agree with him in other important particulars. 



Ihe breathing organs in the adults are usually, as he correctly 

 says, tracheae (I omit the air-sac question at present) ; these tracheae 

 are very long, and so delicate that the slightest attempt to move 

 or separate them, even with the finest badger-hair, usually breaks 

 them, and as they are, as Nicolet says, considerably convoluted, 

 and are interlaced amongst the other organs, I have not found it 

 possible to ascertain with certainty exactly how many there ai-e. 



* Loc. cit., p. 410. 



