. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. 586 Bashford Dean Memorial Volume Nishikawa (I898j states that the yolk has a pinkish color. Presumably his obser- vations were made on fresh material. In our specimens, in various stages of development but not including blastula and gastrula stages, the yolk is usually pale yellov;? but occasion' ally some portions are very pale pink. That Dean had Hve eggs with pink yolk is evi- denced by his two drawings in colorâFigures 49 and 50, plate V. Among Dean's few Chlaynydoselachus slides there are none of either whole mounts o
. The Bashford Dean memorial volume :. Fishes; Sharks; Fishes, Fossil. 586 Bashford Dean Memorial Volume Nishikawa (I898j states that the yolk has a pinkish color. Presumably his obser- vations were made on fresh material. In our specimens, in various stages of development but not including blastula and gastrula stages, the yolk is usually pale yellov;? but occasion' ally some portions are very pale pink. That Dean had Hve eggs with pink yolk is evi- denced by his two drawings in colorâFigures 49 and 50, plate V. Among Dean's few Chlaynydoselachus slides there are none of either whole mounts or sections of the blastula stage. However, there is evidence that, along with the other materials turned over to him by Nishikawa, there were sections of segmenting blasto- derms . In one paragraph of his notebook are a number of rough outline sketches of sections of blastulae labelled "Nishikawa's Slides Early''. Nishikawa (1898, p. 97) portrayed {Text-figure 23) without caption one edge of a segmenting blastoderm but never carried his studies further. Dean had these slides and drew a number of the sections. Among Dean's finished drawings are two, labelled Chlaynydoselachus, which show sections through an early cleavage stage and a late blastula stage respectively. These are reproduced as Text-figures 24 and 25. The magnifications are not given, and the slides from which the drawings were made have been lost. There is nothing very striking about the mode of development portrayed, since it is typically elasmobranch; but Dean in his only pubhcation f 1903) dealing with the development of Chlamydoselachusâa brief noteâcalls attention to "the great depth of the zone of yolk nuclei". This is well shown C 'â¢::â â â .â -â â â â¢- 'V',.'.'. '-^^ ⢠-'-ââ '- .*>! ". .* â â¢-â¢Tt'Jj*". "**-â^â .'â ."â¢^â¢>:~"'.vV.'.-' â "' ^â¢J^v.â¢^:â¢Vâ¢:v^â¢,....-^:;/r^»;::^^^â¢>â¢â¢â¢â
Size: 3158px × 791px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1900, booksubjectfishes, booksubjectfishesfossil
