Norway. 321 



DIVISION XXXVI. 



Ipl. FJELDS PISKERISELSKAB, Bergen. Development of Salmon, 

 Trout and Char, represented by specimens of the parent fish, ova and fry, in spirits. 



192. SARS, PROFESSOR G. O., Kristiania. (Exhibits in the Col- 

 lection of Selskabet for de Norske Fisheries, Fremme). Awarded Paris, 1867, Silver Medal 

 from the Societe d' Acclimation at Paris. (1) Development of the Cod (gadus morrhud'), 

 explained by a series of fifty-six coloured drawings on seven plates, made by the Exhibitor 

 during his visits to the Lofoten Islands in the years 1865-69. PLATE I. Fig. 1. Part of an 

 ovarian sac not fully matured, showing the disposition of the ova in leaf-like clufters con- 

 verging to the interior cavity of ovisac. Fig. 2. Two immature ovicells. Fig. 3. An egg from 

 the ovarian sac, figured No. 1. Fig. 4. Four eggs from a ripe ovisac, showing the blood-vessels 

 ramifying in the surrounding capsules. Fig. 5. A ripe egg protruding from its capsule. 

 Fig. 6. A ripe egg pressed out from the genital duct of a spawny cod. The germinal layer, 

 at first uniformly spread over the yolk, is about to accumulate on the lower pale of the egg. 

 Fig. 6a. Part of the germinal layer of the same egg as seen under a very high magnifying 

 power. Fig. 7. The same egg after having floated some time in the water, without being 

 impregnated, figured in two different aspects. The germinal disc has been formed at the 

 lower pole, but no segmentation has taken place in the same. The small oil-globules of the 

 germinal layer are partly run together in larger globular masses, of which a row surrounds the 

 germinal disc. The micropyle is seen as a small spot in the outer egg-membrane somewhat to 

 the right in the lower part of the egg. Fig. 8. A small portion of a ripe miltsac, showing the 

 finely ramifying bloodvessels. Fig. 9. Spermatozoa as seen through a very powerful micro- 

 scope. Fig. 10. The micropyle-apparatus with the surrounding area, seen from the outer face, 

 highly magnified. Fig. 11. Segment of a ripe egg with the micropyle-apparatus seen in 

 profile, demonstrating the impregnation. Figs. 12-24. Segmentation of the germinal disc. (In 

 Figs. 12-14 and 23 and 24 the egg is figured in two different aspects, so as to exhibit the 

 germinal disc both from the outer face and in profile ; in Figs. 15-22 only in the former 

 position.) Fig. 12. A slight vertical depression has appeared in the middle of the germinal 

 disc, which is surrounded, as in the following stages, by a clear zone. Fig. 13. The depression 

 has taken the form of a distinct furrow on instriction dividing the disc vertically. Fig. 14. 

 The primary segmentation in two halves is completed. Fig. 15. The horizontal furrow has 

 appeared in the two primary divisions. Fig. 16. The disc is divided into four segments. 

 Fig. 17. A vertical furrow has appeared in every one of the four segments. Fig. 18. The disc 

 is divided into eight distinct segments and at the same time has assumed a somewhat oblong 

 form. Fig. 19. The disc is divided into sixteen segments, still forming a single layer. Fig. 20. 

 The segmentation has continued, the disc being now composed of several layers of cellular 

 divisions and showing a more regular form. Fig. 21. The divisions are still more numerous 

 and densely pressed together, assuming a polygonal shape. Fig. 22. The disc is composed of 

 numerous small segments or cells. Fig. 23. The segments are so numerous and small, as to 

 give the disc an almost granular structure. The upper face is still plane. Fig. 24. The 

 segmentation is completed, and the disc has contracted itself and assumed a biscuit- like form 

 the upper face being now strongly convex, while a thin marginal layer of small clear cells has 

 been formed in the segratorial zone of the disc fifth day after impregnation. PLATE II. (2) 

 Formation of the Blastoderm and development of the embryo, 1865. (All the eggs are figured 

 in two different aspects so as to exhibit the embryo both from the dorsal face and in profile.) 

 Fig. 25. Egg on the sixth day after impregnation. The upper convexity of the germinal disc 

 has assumed a somewhat irregular shape, being on one side, where the embryo will develop 

 itself, more prominent. The cells of the disc are about to separate into two distinct layers, the 

 one (epiblast) forming a thinner girdle around the central part. Fig. 26. The embryonal 

 swelling is distinctly seen on the one side. The upper surface or the germinal disc is sunk 

 in the middle so as to give the whole the form of a small cup occupying the lower pole of the 

 egg (the incipient blastoderm), the peripheral girdle being now somewhat denser as the 

 central part. Fig. 27. The blastodorm has been formed, and begins to grow up on the sides of 

 the egg, spreading over the yolk, while the embryonal space advances downwards as a broad 

 triangular lobe, showing at the apex the first appearance of the embryo (the brain and part of 

 the spinal marrow). Fig. 28. The blastoderm has reached the aegratorial zone of the egg, and- 



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