132 



PENTASTOMIDAE. 



with the mouth-parts of the Arthropoda, especially with those of 

 the Acarina, hut such a comparison is hardly permissible on account 

 of the position of this apparatus and its origin in front of the 

 mouth ; it must probably be regarded as a larval organ (Stiles). 

 Near the boring apparatus are two small papillae, which have been 

 regarded as tactile organs (tp). 



The mouth, in P. proboscideum, lies somewhat far back, about 

 on a level with tbe anterior truncated limb (Fig. 58, m). It is 

 surrounded by a chitinous horsesboe-shaped band, and leads into 

 a narrow oesophagus, which passes into a wider stomach. According 

 to Stiles, there is no anus, although one is to be seen in Jacquart's 

 not very accurate drawings. An accumulation of cells surrounding 

 the oesophagus represents the rudiment of the nervous system (m). 

 Stiles also found within the larva a large accumulation of richly 

 granulated cells distributed in a definite manner, some of which 

 are no doubt glandular cells. Two circular structures lying at the 

 bases of the anterior extremities are regarded as the external 

 apertures of glands (so-called stigmata of the glands, Figs. 58 and 

 59, dst). 



The Encysted Larva. The larva which has become free in the 

 intestine of the intermediate host, by the help of the boring 



apparatus at the 

 anterior pole of 

 tbe body and the 

 limbs, traverses 

 the wall of the 

 intestine and 

 passes into the 

 other organs, e.g. y 

 the liver, where 

 it becomes at- 

 tached and en- 

 closed in a fibrous 

 cyst derived from 

 the tissues of the 

 host. It here 

 passes through 

 a number of 



moults, during which it throws off the limbs and the boring apparatus. 

 The caudal appendage also disappears, and the larva assumes a 

 compact cylindrical form. Leuckart found, seven weeks after 



^ ,ma 



ces. 



U-ed. 



Fig. 60. — Encysted larva of Pentmt^mvm tacnioidcs from the viscera 

 of a rabbit, nine weeks after infection (after Leuckart). a, anus ; 

 ag, efferent duct of the genital gland; dst, glandular stigmata; 

 ed, proctodaeum ; gd, genital gland ; m, mouth ; ma, stomach ; n, 

 rudiment of the nervous system ; oe, genital aperture ; oes, 

 oesophagus. 



