43 309 



Visceral anatomy. 



All Syngnathidæ possess 4 complete gills and a well-developed pseudobranchia, 

 consisting of 3 — 4 lamellæ (4 in Siphonostomn, 3 in Nerophis and Hippocampus) of 

 the same structure as those of the branchial arches. The upper gill lamellæ of 

 each row take their origin from the pharyngeal wall, as in Fistularia and Aulostoma. 

 On each side are 5 gill-slits, which do not reach farther dorsally than the cerato- 

 branchial part of the arch; the anterior slit, between the hyoid and the first gill- 

 arch, is much smaller than the following 4. The gill-rakers have already been 

 mentioned, as also the fact that the structure of the gill-lamellæ does not materially 

 differ from that of other teleoslean fishes. For further information about the 

 latter point I may refer to Duméril (12 a, p. 148 and b, p. 480), where the older 

 literature is cited, and to Ryder (48, p. 193) and Huot (19, p. 220). 



The anatomy of the internal organs has been worked out and more or less 

 completely described by several authors, among whom, besides those quoted by 

 Duméril, I might mention Retzius, Kröyer, Lilljeborg and Huot. Here I need 

 only point out, for comparison with the other genera under consideration, that the 

 intestinal canal is simple,* (straight or nearly so in the elongated forms, coiled in 

 Hippocampus), apparently without distinct stomach, the boundary between the 

 stomach and intestine being only marked off by the entrance of the bile-duct, 

 without pyloric appendages and without mesentery (or only with rudiments of the 

 latter, as in Hippocampus, cfr. Moreau (36, p. 30)). The liver is not lobed, provided 

 with a gall-bladder lying in an incision of its right side. The aorta follows the 

 left side of the vertebral column. The air-bladder is present and provided at its 

 anterior end with a "red gland". A urinary bladder is developed. The kidneys 

 show peculiarities hardly found in any other Teleosteans. Such are the complete 

 absence of Malpighian corpuscles (a feature only occurring also in the related 

 genus Solenostomus), the situation of the whole kidney-substance, carrying urinary 

 tubules and both urinary ducts, on one side of the body cavity, the right, following 

 the strongly developed right cardinal vein (the left appears to be absent). Further 

 ought to be noted the fact, that the pronephros or at any rate the large pronephric 

 corpuscle and glomus and the coiled-up anterior part of the pronephric duct, struc- 

 tures so evident in other teleostean larvæ, here appear to be completely absent in 

 the newly hatched larvæ (from the marsupium) and never to be developed later. 

 Also the simple structure of the genital gland in the male, the testis being tubi- 

 form with central canal (cfr. Jungersen 23 a, p. 119, German translation p. 203), is 

 a feature which among many others shows that the Syngnathids have deviated 

 strongly from a normal type and have been highly specialized"--*. 



' A fact already known in 1673 to my countryman Ole Borch (Olaus Borrichils) for Syngna- 

 thus (3 p. 159). 



40* 



