"§> 314. THE ARACHNOIDAE. 387 



CHAPTER VIII. .^ 



ORGANS OF SECRETION. 



/. Urinary Organs. 



§ 314. 



With most Arachnoidae, there are small, usually multiramose, glandular 

 tubes, which open into the cloaca. By their structure and the nature of 

 the fluid they secrete, they exactly resemble the Malpighlan vessels of the 

 Insecta, and like them, also, they have, for a long time, been regarded as 

 hepatic organs ; but now, they are known to be positively those of an 

 urinary nature. The urine is usually accumulated in the cloaca, and con- 

 sists of a troubled, dirty-white liquid, rarely reddish ; and, by direct light, 

 is found to hold in suspension innumerable dark molecules. 



These organs appear to be absent with the Tardigrada, and Pycnogonidae. 

 But, on the other hand, they are easily observed with many Acarina, where 

 they consist of simple or ramose white tubes, situated between the append- 

 ages of the stomach. ^^' With the Phalangidae, there are two pairs of 

 urinary canals which wind between the stomachic caeca. ^-' With the 

 Araneae, these organs are numerous, multiramose, and of a white oi 

 reddish color. Their very small branches penetrate between the different 

 portions of the liver, and end in two principal trunks or ureters, which 

 open into a cloaca provided with a kind of diverticulum.® With the 

 Scorpiooidae, the organization in this respect is quite similar, and the 

 canals, ramified in various ways, enter, some the interstices of the hepatic 

 lobes, while others surround the digestive canal. They pour their product 

 into the cloaca by two ureters which are situated back of the biliary 

 canals.^*' 



1 I have discovered without trouble, these 3 Ramdohr (loc. cit. p. 208, Taf. XXX. fig. 2), 

 canals with the Ilydrachnea, Gamasea, Trombi- and Treviranus (Bau d. Arach. p. 30, Taf. II. 

 dina, and Ixodea. Treviranus (Zeitsch. f. Phys- fig. 24) were only imperfectly acquainted with the 

 iol. IV. p. 189, Taf. XVI. fig. 8, n. n.) had already urinary canals of the Araneae. They have been 

 observed their insertion into the cloaca with Ix- more exactly described bj' Brandt (Mediz. Zool. II. 

 odes. With Ixodes ricinus, where they are p. 89, Taf. XV. fig. 6, 17, or Ann. d. Sc. Nat. XIII. 

 simple and flexuous, I have seen them ascend p. 183, PI. IV. fig. 2, 3) ; but see, especially, /Fas- 

 even to tlie anterior extremity of the cephalo- mann, loc. cit. p. 17, fig. 17, 21-23 (Mygale). In 

 thorax ; this is entirely so with Ixodes ameri- most species, the urine is of a dirty-white color ; 

 canus. Thecanals,whichwithiV/g-Ma, TreD2>an«s but with Mi/g-a/e, it is reddish. In several indi- 

 (loc. cit. fig. 7, g. g.) has regarded as salivary or- viduals of a large species of Mygale preserved in 

 gans, are certainly only the anterior extremities of alcohol, I have found, in the ureters, hard, reddish 

 the urinary vessels. The two species of Ixodes concretions which Dugis (Ann. d. Sc. Nat. VI. p. 

 just mentioned have their cloaca filled with a 180) had already observed. Treated with nitric 

 white urine. acid and ammonia, I obtained purpuric acid. 



2 See Treviranus, Verm. Schrift. I. p. 31, Taf. 4 See Treviranus, Bau d. Arach. p. 6, Taf. I. 

 III. fig. 16, 17. Tulk (loc. cit. p. 249, PI. IV. fig. fig. 6, and Midler, loc. cit. p. 47, Taf. II. fig. 22. 

 17) who has been unable to trace these canals to This last anatomist says that tliese glandular canals 

 their points of insertion on the intestine, has taken communicate with the heart, but he has probably 

 a portion of them for salivary organs. confounded them with the blood-vessels. 



