ANATOMY 311 



which extend backwards, each having five lobes. There are also 

 two median diverticula which proceed from the ventral surface 

 and pass through the endosternite. The abdominal portion of 

 the canal is entirely concealed by the great " liver " mass which 

 comnmnicates with it by four paired ducts in the anterior part 

 of the abdomen. Behind tlie fourth abdominal segment the gut 

 is narrow till it expands in the seventh segment into an hour- 

 glass-shaped stercoral pocket which, according to Laurie, is a 

 portion of the mesenteron. 



The excretory organs are the Malpighian tubes and the coxal 

 glands. The former are generally described as entering the 

 anterior portion of the stercoral pocket, but according to Laurie 

 they pass along its ventral surface, attached to it by connective 

 tissue, and really enter at the posterior end. The coxal glands 

 are well developed, and lie beneath the endosternite, opening 

 near the first coxae. 



The nervous system is much concentrated and of the usual 

 Arachnid type. The median abdominal nerve has a ganglion 

 towards its extremity, supplying, according to Bernard,^ the 

 muscles which move the tail. The heart is extremely long, and 

 varies little in width. It has nine pairs of ostia " — two in the 

 thorax and seven in the abdomen. The generative glands are 

 paired, and in the male there are large seminal vesicles. In the 

 most ventral portion of the abdominal cavity lies a remarkable 

 asymmetrically-situated gland, the " stink-gland." It consists of 

 a number of secretory tubules communicating with two elongated 

 sacs, one of which lies beneath the nerve -cord, and therefore 

 medially, while the other lies far to the left. Their ducts 

 proceed to the anus or its vicinity. 



The caudal organs, or white spots which, as already mentioned, 

 are usually found on the last of the three post-abdominal seg- 

 ments of Thehji^honus, are of doubtful function. They have 

 been variously explained as the stink-gland orifices, and as organs 

 sensitive to light (" ommatoids "). Laurie '^ was unable to find 

 any pore in this region, nor was there any of the pigment so 

 characteristic of organs of sight. The histological structure 

 indicated a sense-organ rather than a gland, but the use of these 

 organs is entirely conjectural. 



1 Tr. Linn. Soc. (2) vi., 1896, p. 344. ^ Bernard, loc. cit. j). 366. 



^ J. Linn. Soc. xxv., 1894, p. '29. 



