222 



The youngest, newly-hatched, animals, I found, were short-legged, 

 mite-like individuals of a size of hardly ^4 mm, their longest, second 

 ambulatory, leg about 5 mm. The tracheal system of the body is fully 

 developed and easily found. It is far more difficult to find the two 

 thin branches, which penetrate each leg between the muscles of the 

 femur. I succeeded however to follow their running towards the tibia, 

 where the branches became too small and escaped observation. Ex- 

 ternal openings on the tibiado notexistin these young 

 animals. Even in the much larger individuals from 3 — 5 mm, when 

 the legs are greatly elongated and have nearly attained their full 

 length, no trace of spiracles could be found, neither on the skin, nor 

 on the tracheae within the tibia. In two or three of these larger ani- 

 mals, however, when seeking for the external opening, I observed in 

 optical section of the leg, on the spot where, in the adult, the proximal 

 stigma might be expected, a large, oblong, but thin-walled cavity 

 beneath the skin. This cavity communicated by a very short air-tube 

 with the tracheal trunk in the posterior part of the tibia, which is 

 running very near. 



Though many sections of the legs were prepared and carefully 

 examined, yet they gave but negative results, owing to the difficulty 

 of impregnating and the impossibility of maintaining the inner parts 

 of the legs in their respective places. From the few facts, as stated 

 above, we may, however, evidently deduce, the Opilionidae have true 

 post-embryonic spiracles on the legs, which take their origin 

 from the tracheae within the tibia at a time, when the feet are rapidly 

 growing and the supply of air in those slender limbs becomes difficult. 

 The next time the animal casts its skin, the external opening of the 

 stigma will probably be formed by perforation of the tracheal cavity. 



Though is seems therefore very clear, that want of air in the long 

 legs is the principal causal moment, still many long legged Opilio- 

 nidae of other families possess no spiracles, whereas they are always 

 found even in the short-legged genera of the Family Phalangioidae. 



II. Mittheilungen aus Museen, Instituten etc. 



1. Zoological Society of London. 



2l8t April, 1896. — The Secretary read a report on the additions 

 that had been made to the Society's Menagerie during the month of March, 

 and called special attention to a fine young female Gorilla {Anthropopithecus 

 gorilla)^ from French Congoland, obtained by purchase; a young male Mark- 

 hoor [Capra meffaceros), from the vicinity of Peshawar, British India, presen- 

 ted by Col. Paterson, March 18th; a pair of a rather scarce species of Duiker 

 Antelope [Cephalophus coronatus)^ from West Africa, purchased; and a 

 Silver-backed Fox [Canis chama), from Cape-Colony, presented by C. W. 



