^ 314. THE ARACHNOIDAE. 887 



CHAPTER yill 



ORGANS OF SECRETION. 



I. 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 Malpighian 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 or 

 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 

 Scorpionidae, 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 

 «anals.*^^ 



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



canals with the Hydrachnea, 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 by Brandt (Wediz. Zool. II. 



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



«imple and flexuous, I have seen them ascend p. isiä, PI. IV. fig. 2, 3) ; but see, especially, fVag- 



■even to the 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 j 



■canus. The canals, which with iV!g'Ma,TreDirani/s but with il/yfi-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 Myp;ale preserved in 



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



tlie urinary vessels. The two species of Ixodes concretions which Duges (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. 



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



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



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



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



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



