30 Mr. H. J. Carter on a Bisexual Nematoid Worm 



every third Fly contains from two to twenty or more of these 

 worms, which are chiefly congregated in, and confined to, the 

 proboscis, though occasionally found among the soft tissues of 

 the head and posterior part of the abdomen. They are bisexual, 

 have arrived at maturity, and are all nearly of the same size ; and 

 as they are perhaps more nearly allied to the Filaridse than to any 

 other family of the Nematoid worms, it seems best to place this 

 worm, at all events for the present, in the genus Filaria, where, 

 with the specific designation of " ilf i<sc«," its description may 

 stand as follows : — 



Filaria Muscce, n. sp. PI. I. A. figs. 1 and 2. 



Linear, cylindrical, faintly striated transversely, gradually 

 diminishing towards the head, which is obtuse and furnished 

 with four papillae at a little distance from the mouth, two above 

 and two below ; diminishing also towards the tail, vi'hich is short, 

 and terminated by a dilated round extremity covered with short 

 spines. Mouth in the centre of the anterior extremity. Anal 

 orifice at the root of the tail. 



Oesophagus comoiencing from a slightly dilated oral orifice, 

 narrow at first, then becoming suddenly increased in calibre, 

 and, after extending some distance backwards, joining the intes- 

 tine, apparently without any line of demarcation, opposite the 

 anterior termination of the hepatic organ. Intestine continued 

 straight through the body, and nearly of the same size, on to 

 the rectum, which is short and obliquely directed towards the 

 anus. CEsophageal sheath (fig. 3 d) commencing at the termi- 

 nation of the narrow portion of the oesophagus posteriorly, where 

 the latter is embraced by the dorsal vessel, gradually increasing 

 backwards to join, without a line of demarcation, the sheath of 

 the intestine, which, on its part, soon attaining its maximum 

 calibre, is continued backwards, of the same size, to the termi- 

 nation of the hepatic organ, where it becomes slightly but sud- 

 denly reduced in diameter and afterwards maintains nearly the 

 same size, on to the rectum. 



Hepatic organ (PI. I. fig. 2 d) marked by a dense white layer 

 of oil-globules and granular matter within the intestinal sheath, 

 surrounding the anterior third of the intestine, commencing op- 

 posite the union of the latter with the CEsophagus, and termi- 

 nating at the sudden diminution iii diameter of the intestinal 

 sheath, where it is defined by a circular line (m). Rectum (o) 

 more or less obscured by muscular and other structure, in the 

 midst of which two glandular bodies are observed opposite its 

 junction with the intestine. Dorsal vessel [e e e) extending 

 from the point of union between the smaller and larger portions 

 of the oesophagus (e), which it embraces by bifurcation, to the 



