400 REPORT ON ZOOLOGY, MDCCCXLIV. 



OPILIONES. 



OPILIONIDES. A new genus, Phalangodes, has been characterized by 

 Tellkampf. (Wiegm. Arch. IS 44, i, 320, pi. 8, f. 7-10.) It is distinguished 

 by the prickly palps, and above all by the want of eyes. The species, Ph. 

 armata, which is half a line in length, is found in the Mammoth cave in 

 Kentucky. 



ACARL 



Dujardin has laid before the Academy of Paris his researches concerning 

 the organs of the mouth, and the internal structure of mites, Sur les 

 Acariens, et eu particulier sur les organes de la manducation et de la 

 respiration chez ces animaux, ler Mem. (Comptes rend, xix, 1158.) In 

 the mouth he has distinguished a variety of modifications. As to the 

 alimentary canal, he has not been able to make it out, and he infers that the 

 organic fluids which form the food of mites pass into the cavities of the 

 parenchymatous mass, which is of the nature of a liver. In Bdella, 

 Gamasus, Dermanyssus, all blood-suckers, there is found indeed an internal 

 chamber with symmetrical lobes filled with blood, but even here no closed 

 vessel can be demonstrated, and the fluid seems merely to occupy the spaces 

 between the muscles of the legs. They have, however, an anal opening. 

 Specific secretions are found ; e. g. Trombidium has a pair of poison- or 

 saliva-vessels, which open by a long excretory duct into the ends of the 

 mandibles. Respiration goes on simply through the skin in Acarus and, 

 Sarcoptes, while in Gamasus, Cheyletus and various kinds with piucer-shaped 

 mandibles, there is a complete system of trachea with spiracles as in true 

 insects. Besides these two, there is an intermediate plan of respiration 

 not known before, combining both the other modes, in which inspiration 

 takes place through the skin, and expiration through a system of trachea 1 , 

 which have their outlet above the insertion of the mandibles. Trombidium 

 is given as an example, in which a latticed aperture at the root of the 

 mandibles forms the anterior outlet of two large air-pipes running from the 

 hinder end to the front, each subdivided into a tuft of numerous unbranched 

 simple tracheae. Besides these there is under the skin a round-meshed 

 network of a transparent and seemingly homogeneous substance, resembling 

 the respiratory net under the skin of certain Trematoda. This tissue, in 

 conjunction with the coat of feathered hairs, is supposed to serve for 

 inspiration of air (absorption des elemens gazeux.) The water-mites are 

 similarly circumstanced, having a corresponding system of trachea?, the 

 single anterior orifice of which cannot serve both for inspiration and renova- 

 tion of the air. In these tribes LimnocJiares, Atax, Hydrachna, Limnesia, 

 stomata are found, like those of plants, disseminated over the entire surface, 



