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. R. Semon! has made observations in Queensland 
on the habits of Arius australis, which builds nests in the sandy 
bed of the Burnett River. 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, 
Galeichthys,? and Osteogeniosus,;’ the male, more rarely the female, 
carrying the eggs in the mouth and pharynx; these eges, 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, Walopterurus 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, Si/urus 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 anda 
weight of 400 lbs. 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 5 or 4 in diameter, which is believed to enter and 
ascend the urethra of people bathing, being attracted by the urime ; 
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.” According 
7 ¥ 
1 Zool. Forsch. Austral. v. ii. 1895, p. 273. See also Wyman, 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. y. Ihering, Biol. Centralbl. viii. 1888, p. 298. { 
3 Cf. Boulenger, P.7.S. 1891, p. 148. 4 Cf. Day, Fish. Ind. 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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