Observations on the Oribatidse. By A. D. Michael. .9 



to a bilobed form, in which case they extend down the side of the 

 ventriculus as far as their size renders necessary ; they are composed 

 of large, loosely aggregated cells, and are easily broken up if 

 disturbed in most species. Two similarly placed glands appear to 

 exist in such Vermes as Prorhynchus jluviatilis. 



It was some considerable time before I could trace the ducts 

 from these glands at all to my own satisfaction, they are usually so 

 very delicate that it is extremely difficult to detect them, and, 

 although 1 thought that they followed the course which I now 

 suppose to be correct, yet I could not feel any certainty. After 

 trying numerous species I experimented on Leiosoma palmicindum, 

 in which I was pleased to find the ducts apparently more distinct ; 

 they seem, as far as I can at present judge, to run in an almost 

 straight course along the surface of the ventriculus, which they 

 appear to enter just above the cseca (this is shown in plate I. 

 fig. 4, n), where they are delineated as separated from the ventriculus 

 by dissection. If this course of the duct be correct, the office of these 

 glands is doubtless the secretion of some fluid useful in digestion. 

 The point cannot yet be considered as decided, as the glands have 

 some attachment to the outer wall of the body. I have since found 

 that they are equally well seen in Notaspis lucorum. Probably, 

 if Burmeister's views were to be followed, these glands, from the 

 place where their ducts seem to discharge, should be called pan- 

 creatic, but as the Oribatidse are vegetable feeders the function 

 would not be analogous. The glands and ducts possibly form the 

 homologues of one pair of the anterior cseca of the ventriculus 

 present in so many of the Arachnida. 



The dorsal part of the anterior portion of the ventriculus and 

 of the whole of the cseca is usually covered with a thickish layer of 

 brown foUicular-looking cells, which sometimes entirely cover the 

 dorsal surface of the ventriculus. I cannot say that I have ever 

 succeeded in detecting any ducts from this mass ; they would 

 doubtless be very fine, but I think that they are identical with 

 those which many authors have considered as having a hepatic 

 function. Thus Megnin, in his able treatises on the Gamasinm* 

 and on the Sarcoptidw of mammals, says that he regards this 

 brown granular substance as being analogous to that which coats 

 the hepatic tubes of insects, and as being in fact the liver. A 

 similar organization in many annelids was pointed out long since 

 by Quatrefages,! who assigned it a similar office. Claparede speaks 

 of the ventriculus, &c., and coating of cells as the " lebermagen " 

 in the Hydrachnidse, and that most careful anatomist, Cronberg, 



* " Memoire sur I'organisation et la distribution zoologique des acariers de 

 la famille des Gamasides," Jomn. Anat. et Phys. (Eobin) 1876, p. 315. " Mono- 

 giraphic de la tribu des Sarcoptiiles psoriqiie," Revue et Mag. de Zool., 1877, p. 157. 



t " Memoire sur quelques Planariees marines," Ann. des Sci. Nat., 1845. 



