OCR Text |
Show 1 894.] CURVATURE OE T H E SPINE IN EISHES. 97 total length, in this specimen it is nearly ^rd of that \ The haemal and neural arches of this specimen are normal, except for a marked flexion forwards of the neurals numbering 20 to 24. Another instance of curvature of the spine in the Sole, for which I a m indebted to the Eoyal College of Surgeons, is that traced in fig. 2. This ease differs most conspicuously from both the foregoing in the acuteness of the first two sinuosities, and in the fact that at each vertex there is a slight displacement to the left side, which in all probability involved the body as a whole. Except for the first eight neurals, which are very aberrant, the arches had so adapted themselves to the situation as to have maintained the normal regularity of contour of their extremities ; and the only lesser detail worthy of remark here is the presence of synostotic enlargements 2 on the neural spines 9, 10, and 11. 48 vertebrae in all are present. Synostosis of the vertebrae of fishes has been recorded by Erdl and Stannius 3. While it is most generally regarded as confined to the opposite extremities of the spine, O w e n has pointed out4 that in Pleuronectidce " a kind of sacrum is formed by such bony union of the bodies of the first two of the caudal series." Examination of a series of Pleuronectid skeletons will easily convince anyone that this is an inconstant feature. The most important monograph on the subject is to be found among Hyrtl's classical contributions to the Vienna Denkschriften5. In a short preliminary communication which immediately preceded the aforesaid monograph, Hyrtl remarked6 that "the number of co-ossified vertebrae is 2 to 6," and that " this synostosis takes place more frequently in the tail than in the trunk "-while, commenting on the probable ill effects of the malformation, he naively points out that diminution in flexibility is, at any rate in some cases, " obviated by the fact that the confluent vertebrae are not larger than the non-confluent ones, their length being so much reduced that the five coalesced vertebrae are not longer than one and a slight fraction of a non-coalesced one." In his second monograph he has described certain conditions to which this fascinating argument will not apply, for example that of a Codfish in which the six co-ossified vertebrae occupy a greater area than the two which precede them. One of the aforementioned specimens which Prof. Sutton has 1 Length 8f in., greatest vertical diameter 2| in. 2 I have in no instance observed these on the hasinal side. 3 By Stannius in Amice (Handb. d. Zootomie, Aufl. 2, Th. i. p. 21). His record of the fusion of ''intercalary with true vertebrae" becomes one of synostosis of vertebral bodies, from Schmidt's discovery (Zeitschr. wiss. Zool. Bd. liv. p. 748) of the truly vertebral nature of the so-called inter-centra of this animal. 4 Comp. Anat. of Vertebrates, vol. i. p. 42. 5 " Ueb. Wirbelsynostosen und Wirbelsuturen bei Eischen," Wien. Denkschr. xx. 1862, pp. 95-110. 6 Nat. Hist. Eeview, vol. ii. 1862, pp. 103-104. PROC. ZOOL. Soc-1894, No. VII. 7 |