xxi OSTARIOPHYSI 593 



accordance with these pairing habits, the pectoral spines of the 

 male, which are used in amplexation, are longer and stronger 

 than those of the female. These Fish are monogamous, and both 

 parents remain by the side of the nest, furiously attacking any 

 assailant. Dr. E. Semon l has made observations in Queensland 

 on the habits of Arius australis, which builds nests in the sandy 

 bed of the Burnett Eiver. These nests consist of circular basin- 

 like excavations, about 20 inches in diameter, at the bottom of 

 which the eggs are laid, and covered over by several layers 

 of large stones. A still more efficient protection is afforded 

 their progeny by the marine and estuarine species of Arius, 2 

 Gcdeichtliys? and Osteogeniosus, 4 the male, more rarely the female, 

 carrying the eggs in the mouth and pharynx ; these eggs, few in 

 number, are remarkably large, measuring as much as 17 or 18 

 millimetres in diameter in Arius commersonii, a Fish of three or 

 four feet in length. According to Babuchin, Malopterurus also is 

 said by the Nile fishermen to shelter its fry in the mouth. 



Some of the Silurids attain to a very large size. Among these is 

 the type of the family, Silurus glanis, the " Wels " of the Germans, 

 its only European representative, which occurs over a great part of 

 Europe, but is absent from the British Isles, France, the Spanish 

 Peninsula, and Italy. It is most abundant in the Danube basin, 

 where it sometimes reaches a length of 10 feet or more and a 

 weight of 400 Ibs. It is the largest strictly fresh- water Fish of 

 Europe. Among the smallest species, we have to mention the 

 " Candiru " of Brazil, Vandellia cirrhosa, 60 millimetres in 

 length and 3 or 4 in diameter, which is believed to enter and 

 ascend the urethra of people bathing, being attracted by the urine ; 

 the Fish, having once made its way into the urethra, cannot be 

 pulled out again, owing to the erectile spines which arm its gill- 

 covers. The natives of some parts of the Amazons are in great 

 dread of this Fish, and protect themselves when entering the 

 water by wearing a sheath formed of a small, minutely-perforated 

 cocoanut-shell suspended from a belt of palm-fibres. 5 According 



1 Zool. Forsch. Austral, v. ii. 1895, p. 273. See also "VVyman, Amer. Journ. 

 Sci. (2) xxvii. 1859, p. 12 ; Hensel, Arch. f. Nat. 1870, p. 70 ; Turner, J. Anat. 

 and Physiol. i. 1867, p. 78. 



2 Cf. H. v. Ihering, Biol. Centralbl. viii. 1888, p. 298. 



3 Cf. Boulenger, P.Z.S. 1891, p. 148. 4 Cf. Day, Fish. bid. 1878, p. 456. 

 5 Cf. Boulenger, P.Z.S. 1897, pp. 901 and 920 ; Jobert, Arch, de Parasitol. i. 



1898, p. 493. 



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