Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1890 edition. Excerpt: ... The figures of the young of A. ruthenus, the sterlet, given by Zograff, Figs. 19, 20, and 21, show that the dorsal scutes are developed before the lateral or ventral. This is also shown by the young of A. huso, figured by Brandt and Eatzeburg, but in not so marked a manner. The young of A. ruthenus, figured by Zograff, also shows that the scutes develop from before backwards. That is to say, there are as yet no fulcra shown on the dorsal margin of the tail, nor does the lateral series of scutes extend much beyond the vertical from the anterior end of the dorsal, as seen in Fig. 21. The tail is, in fact, fringed above and below only by fin-fibers or actinotrichia, such as are usually the supports of the fins of young fishes. The narrow scutes or overlapping fulcra of the dorsal margin of the tail are developed later, and derive their origin in the main from tissue elements which lie deeper than those which give origin to the actinotrichia and ultimately to the fin-rays proper of the adult. I am not inclined to agree entirely with Zograff as to the method in which the dorsal scutes are developed, as given In No. 29, cited in the list of papers at the end ot this monograph. In other fishes the actinotrichia or fin-fibers become embedded in the calcifiable matrix deposited around them, as my studies upon the development of the fin-rays of the salmon prove. That the scutes of the dorsal median line in sturgeons do develop partly at the expense of the embryonic fin-fibers is doubtless a fact, but that they are the sole basis of origin of the calcifiable matrix of the scutes in these forms does not seem probable, judging by what is known of the rays of other types. The so called "fulcra" of the lower side of the caudal, at its anterior end, are...
