1014 REPOET OF COMMISSIONER OF FISH AND FISHERIES. [34J 



than tbe permanent rays, as shown in Fig. 1, PI. IX; (4) these structures 

 are found at about the close of the lophocercal stage in both the paired 

 and unpaired iins and in the same relation to the integument in both, and 

 form a perfectly continuous series when the folds are continuous; (5) 

 they either atrophy together with the atrophied portions of the median 

 folds, or they persist as in the adipose fins of Salmo, Amiurus, &c., or 

 they coalesce and become enveloped by a homogeneous substance (Fig. 

 10, PL IX) to form the permanent rays, or they become more or less 

 covered by the mesoblast, and some finally atrophy ; (G) they are per- 

 fectlj" homogeneous, as shown in Fig. 11, PL IX, and are in every re- 

 spect similar, optically and histo-chemically, to the perichondrium as 

 developed around the chorda, cartilaginous ribs, and spines, or the ho- 

 mogeneous hyaline membranes in which the membrane bones of fishes 

 form and calcify. 



The fact that these fibers coalesce proximally to form the matrix of 

 the permanent rays in Teleosts is positive proof of the fact that the 

 numerous horny fibers found in the fins of Chimaeroids, Sturgeons, Pla- 

 giostomes, and Dipnoans, are almost exactly homologues of the osseous 

 rays of the first mentioned, supplemented as such a conclusion is by the 

 fact that in all of these, as shown by evidence gathered by Balfour, Giin- 

 ther, and myself, the relations of the fibers to the epidermis and meso- 

 blast is fundamentally the same in all; that is, the fibers occupy exactly 

 the same place in respect to the other tissues in the fin-fold as do the 

 two halves of the rays of the fully-developed fins of Teleosts. The fibers 

 being parallel, numerous, and developed in a form which develops a 

 skeleton in a coelacanthous manner at first, which in its later cartilagin- 

 ous condition at the close of the lojihocercal stage resembles more than 

 any other the condition which is permanent in Protoptervs or Gerato- 

 dm, leads me to the conclusion that this stage of the larvjie of osseous 

 fishes may very appropriately be called the Protopterus or Protojptery- 

 (jian Htage on account of the remarkably close resemblance of its fin- 

 system to the archaic type of fins possessed by the Dipnoans, whi<;h 

 unquestionably preceded the Teleosts in time. 



We thus get a more satisfactory notion of the relation in which these 

 forms stand to each other. And we must now, for obvious reasons, 

 regard the rays of Teleosts as merely a more highly specialized condition 

 which ontogeny has shown must have arisen from a stage which is per- 

 manent in the Dipnoans, forms strangely advanced in some respects 

 while they have remained singularly embryonic in almost every other. 

 We thus find that the parallelism which has been insisted upon as exist- 

 ing between Palasozoic forms on the one hand, and the young stages of 

 osseous fishes on the other, by L. Agassiz and Vogt, and also by A. Agassiz, 

 is warranted in its main features, when all of the facts are produced which 

 ontogeny has to offer, though it is true that it will not do to push the 

 comparison too far. We are also enabled to say with some certainty 

 that the distal cartilages of the paired fins upon each side of which the 



