WERNER MARCHAND 37 



two globules, four evidently having been expelled. At about the same 

 time another larva of the same age was found to contain only the 

 two bodies of anterior cyst; all the others had been thrown out.® 

 In summarizing Lecaillon states: 



(1) The black bodies are formed by the cellular mass which constitutes the 

 fundus of the capsule. (2) The globules are detached periodically to be expelled 

 to the exterior after a longer or shorter time. (3) They are regenerated at the 

 bottom of the cyst when the others have been expelled. 



These conclusions of Lecaillon appear only partly warranted. 

 From observations made hitherto there is no indication of a relation 

 of the discharge of these bodies and their new formation. 



Concerning the nature of the black bodies, Lecaillon states that they 

 are not hard as if they were mineral granulations ; they are not affected 

 by reagents, as acid fixation fluids; they may be cut when the organ is 

 sectioned. Consequently they seem to be a pigmented material, 

 excreted by the cellular mass which forms the bottom of the cyst. 

 Lecaillon alludes, in suppport of this view, to the fact that the larvas 

 of Tabanus quatiwrnotatus have a completely white body though the 

 substances found in the digestive tract (organic relics) are usually 

 blackish. The pigment derived from the alimentary substances, or 

 formed normally in the body, might be excreted by means of this 

 particular gland. 



Paoli in Florence in 1907 studied the same organ in various taba- 

 nid larvce which, on the authority of Bezzi, are said to belong prob- 

 ably to Tabanus cordiger Meig. or Tabanus autumnalis L. Paoli, 

 however, asserts that in all probability many species of this family 

 possess Graber's organ more or less developed and also with slight 

 modifications in details of structure, according to age and species. 

 For the description of the larvae studied by Paoli see pages 91-93, 

 Tabanus autumnalis. 



According to Paoli's description, Graber's organ is found in the vis- 

 ceral cavity, situated dorsally under the subcutaneous muscular strata, 

 in the anterior third of the eighth abdominal segment between the 

 two large tracheas (Plate 10, Figs. 115 and 116). It is a little pear- 



® I have been able to confirm Lecaillon's observations in the larvae of Tabanus 

 atratus (1916). 



