. Carnegie Institution of Washington publication. 164 Papers from the Marine Biological Laboratory at FlG3. I AND 2.—Longitudinal sections of the advanced planulae, showing the columnar ectoderm, the more or less solid endoderm, containing irregular or radiating cavities, and the ectodermal invaginations which lie between the ectoderm and endoderm and are of doubtful significance. An ectodermal invagination at the narrower pole of fig. 2 may represent the stomodaeal invagination. As compared with the development of other medusje, the entire enihry- ology of Liiiergcs is characterize
. Carnegie Institution of Washington publication. 164 Papers from the Marine Biological Laboratory at FlG3. I AND 2.—Longitudinal sections of the advanced planulae, showing the columnar ectoderm, the more or less solid endoderm, containing irregular or radiating cavities, and the ectodermal invaginations which lie between the ectoderm and endoderm and are of doubtful significance. An ectodermal invagination at the narrower pole of fig. 2 may represent the stomodaeal invagination. As compared with the development of other medusje, the entire enihry- ology of Liiiergcs is characterized by the regularity of the processes of cleavage and gastrulation; and although this regularity may sutler certain modifications, without preventing the formation of a normal planula, there is in this species none of that extreme irregularity which characterizes the development of Pcnnaria (Hargitt. 1904). EXPERIMENTS. Isolation of blastomercs.—My observations on the development of parts 01 the unsegmented egg and of isolated blastomeres are essentially similar to those of Zoja (1895) and Maas (1905). Parts of the unsegmented but fertilized egg may give rise to swimming larvae; these are almost certainly the parts containing the egg and sperm nuclei. Isolated blastomeres, at least as late as the 4-cell stage, give rise to swimming larvae, which are ap- parently normal; however the lack of clearly dififeraitiated organs in the planula makes it difficult to determine in this stage whether the larvae are wholly normal or not. When the egg fragments are small, or when the blastomeres are isolated at a late stage of the cleavage, the blastocoel is rela- tively small and the gastrulation is not normal. These results are essentially like those obtained by all investigators of the development of the Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations
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