S80 THE ARACHNOIDAE. <§> 308. 



tube, of nearly equal size throughout, without a stomachic dilatation and 

 M'ithout caeca, which opens by an anus at the posterior extremity of the 

 body.<^' 



§ 308. 



Tlie Salivary glands exist with, perhaps, all the Arachnoidae ; for, they 

 are found even in many of the lower forms, where their presence would be 

 least expected. With the Tardigrada, there are on each side of the suck- 

 ing apparatus, large, lobulated glandular tubes, which appear to be organs 

 of this nature, although their outlets have not yet been distinctly traced. ^^> 

 With the Oribatea, there is at the anterior extremity of the body, a pair 

 of similar tubes, but simple and colorless, which extend to the mouth, 

 and have undoubtedly a salivary function.*-* 



With Ixodes, these organs are extraordinarily developed, consisting of 

 two large masses of vesicles situated on the sides of the anterior part of the 

 body, and opening by short ducts into two niultiramose excretory canals. 

 These last, whose walls are traversed by a solid spiral filament, open into 

 the buccal cavity at the base of the lip-like process.'^' 



With the Araneae, a slit in the upper lip leads into a cavity situated 

 .above the palate, and at the base of this cavity is a transparent, glandular 

 äuass, which, very probably, secretes the saliva ; this flows up through the 

 .slit in question, and moistens the substances from which the animal ex- 

 tracts its food.'''* As salivary organs should also be considered the two 

 pairs of glandular tubes, which, with the Scorpionidae, are situated on the 

 sides of the anterior part of the body, and extend forwards to open into 

 the oesophagus.'^' 



With the Araneae, and Scorpionidae, there is a Liver distinct from the 

 digestive tube, which, for a long time was regarded as an adipose mass. 

 With the Tardigrada, Acarina, Pycnogonidae, and Opilionina, the walls of 

 the stomachic appendages are of this nature, for they are glandular and com- 

 posed of granuhir and usually yellowish-brown cells.'"' With the Araneae, 

 the brown or dirty-yellow liver is very voluminous, filling a large portion 

 .of the abdominal cavity, and enveloping most of the other viscera. 



At first sight, it appears to be a compact mass, but, further examined, 

 5t is found composed of numerous multiramose, closely-aggregated caeca. 

 The walls of these are thick, and crowded with hejratic cells, and they open 

 into the digestive canal near its middle by four short hepatic ducts.'"^* 



9 With the Scorpionidae, the anus is situated on * See Müller, loc. cit. p. 52, and Newport, 



the penultimate caudal segment. Philosoph. Trans. 1S43, PI. XV. fig. 39. 



1 See Doyire loc. cit. p. 321 PI. XIII.-XA^. ** With the Tardigrada, Acarina, and Opilionma, 



2 I have seen 'these glandular tubes fiiih Hoplo- ^t ''^'*st, I have seen, distinctly, hepatic cells in 

 phora Zetes and Oribates. '^"^ walls of the stomachic appendages. See also 



■i The .salivary glands of Ixodes ricinus resem- Doyire, loc. cit. p. 327, PI. XV. 



ble exactly the botryoidal ones of many of the In- ' Treviranus (Bau d. Arachnid, p. 30, 47, Taf. 



«BCta. •' ' II. fig. 24, dd., and Taf. V. fig. 47) had already 



The secretory vesicles of the saliva are filled with observed the communication between the liver and 



transparent nucleated cells and surrounded by t'"-' <li!?estive organs. The remaining points in the 



numerous ramified tracheae with which it is im- .structure of this organ have been rightly estimated 



possible to confound the excretory ducts of these ^'Y Dugis (Ann. d. Sc. Nat. VI. p. 179), Grube 



t'lands; for with these last the spiral turns of thin ('"c- c"-- P- 299), and H^asmann (loc. cit. p. 13, fig. 



filament are very wide apart, while, in the tracheae, I'l '"• ";' '^^-'^'^}- . See also Owen, Lectures, kc, 



the sjjiral windings are very close together. P- '^^'^i *iS- H^*) '• •• 



•1 This glandular a|)iiaratus has been seen by 

 iVa.imanii (loc. cit. p. 8, fig. 16) with Mygale ; 

 1 have found it also with other Araneae. 



