46 Alimentary Canal 



groove on cephalothorax, which marks the boundary between head and thorax. With 

 regard to this point we refer to our remarks on pp. 5, 6 concerning the boundaries of 

 cephalothorax and the two last thoracic segments belonging to it. 



8. Remarks as to the other interior Organs. 



The information hitherto available on the interior anatom}' of Opiliones is very limited 

 and refers only to a few species. Amongst Laniatores the anatomy of only three species 

 has been published by William Sorensen (6), these belonging to the two families Gonylep- 

 toidse and Cosmetoidaa, which are not nearly related to each other'. Amongst Palpatores 

 scarcely any have been examined respecting their interior structure, except the commonest 

 European harvest spiders which belong to Phalangioidse. The principal authors as regards 

 this family are Treviranus, Tulk, Loman (a), and, on the subject of the alimentary canal, 

 Plateau. The sexual organs of Phalangioidse alone have been repeatedly examined by 

 Lubbock, Krohn (a), Blanc, de Graaf, and Sorensen (c), the principal paper being that 

 of de Graaf Only a few scattered notices have been published by Lubbock and Sorensen (c) 

 concerning a few species of other families than Phalangioidaa. As the terminal parts of 

 the sexual organs offer characters of special systematic value, we have especially endeavoured 

 to supplement the knowledge of these organs in Laniatores and Palpatores, by means of 

 fresh investigations. Concerning the inner structure of C3"phophthalmi no information has 

 jret been published. Unfortunately the specimens which we have been able to examine 

 were not in such a state of preservation, that we could enter on an investigation of the 

 histological structure of the organs ; even in the topographical anatomy of these animals 

 there are several points on which we could have wished to give fuller information, and 

 the anatomy of the dorsal vessel and the nervous system we have not been able to study. 

 Nevertheless, we venture to hope that what we have to communicate will prove of interest, 

 and particularly that it will serve to fix the diagnosis of the order and its sub-orders 

 respectively. 



9. The Alimentary Canal. 



The alimentary canal, which is straight in all Arachnida, consists, according to Plateau 

 and Loman {a, p. 3-t), in Palpatores of four divisions : a narrow oesophagus, a small anterior 

 portion, a wider and capacious middle portion, the mid-gut, which is the largest part of 

 the alimentary canal, and a less capacious anal portion. In Laniatores and Cyphophthalmi 

 the alimentary canal consists probably of the .same divisions of similar dimensions, because the 

 fact that Soren.sen did not notice the anterior portion in Laniatores, and that we have not 

 observed it in Cyphophthalmi, is no doubt owing to the small size of that division. 



The most remarkable feature of the alimentary canal in Opiliones is the presence of 

 the large diverticula which branch off from the anterior part of the mid-gut and which 

 are joined by connecting tissue to the sides and dorsal surface of this as well as of the 

 anal division, so that these divisions are covered by diverticula, excepting a broader or 

 narrower part of their under surface, and thereby often assume a strange appearance. In 



' Loman mentions that he has studied the anatomy of other families of Laniatores, but he has not yet published 

 more than a single result of his investigations. 



