EXPLANATION OF PLATE II. 



Fig. 1. Vertical section of the tail of Alosa sajridiasima 22 days old ; s superior, i infe- 

 rior border, hy hypnral cartilages, ch cborda surrounded by connective and 

 muscular luesoblaatic tissue, x 65. 



Fig. 2. Tail of ^?osa sapidissima 4 dnyn afler batching, showing the striate caudal 

 fold cf. The direction of the stride correspond to the direction in which 

 growth has manifested itself, and seems to be an eftect of the development 

 of the embryonic rays. The myotomes jn^/ are shown to be faintly devel- 

 oped almost to the end of the tail, but there is a space on the side from o 

 to o' where muscular tihsue has degenerated and is not present, so that the 

 voluminous chorda lies in immediate contact with the ekin at this point. 

 The hypnral elements arc just forming and are shown to be related to cor- 

 responding somites ; their bases have pushed the ventral wall of the chorda 

 inward slightly. From a balsam preparation, x 64. 



Fig. 3. Epural and hypural cartilages ofthe tail of the California salmon, Oncorhynchns, 

 with the accessory basilar pieces h' in outline; these are developed later. 

 X 32. From a specimen cleaned in a 5 per cent, potash solution and ren- 

 dered transparent with glycerine. 



Fig. 4. Vertical section through the tail of an advanced embryo land-locked salmon ; 

 8 superior, i the inferior nuirgin, /i// hypural pieces, ch end of chorda, ci; cau- 

 dal vein, ao aorta, r rays cut across and composed of homogeneous material, 

 (Ig unicellular dermal glands, or goldet cells. The permanent rays ?• are cut 

 across at their proximal ends, and it is evident that they are imbedded iu 

 mesoblast. x 32. 



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