Entocodon sentence example
- It is marked by the formation in the bud of a characteristic structure termed the entocodon (Knospenkern, Glockenkern).
- The entocodon is usually formed, proving the medusoid nature of the bud, but in sporosacs the entocodon may be rudimentary or absent altogether.
- It is seen from the foregoing account of medusa - budding that the entocodon is a very important constituent of the bud, furnishing some of the most essential portions of the medusa; its cavity becomes the subumbral cavity, and its lining furnishes the ectodermal epithelium of the manubrium and of the sub-umbral cavity as far as the edge of the velum.
- The entocodon is to be regarded, therefore, not as primarily an ingrowth of ectoderm, but rather as an upgrowth of both bodylayers, in the form of a circular rim (IVa), representing the umbrellar margin; it is comparable to the bulging that forms the umbrella in the direct method of budding, but takes place before a manubrium is formed, and is greatly reduced in size, so as to become a little pit.
- To sum up, the entocodon is a precocious formation of the umbrella, closing over to protect the organs in the umbrellar cavity.Advertisement
- The possession of an entocodon proves the medusa-nature of the bud,.
- Especially noteworthy in the germinal budding of Margellium is the formation of the entocodon, as in the vegetative budding of the indirect type.
- The medusa arises direct from the actinulastage and there is no entocodon formed, as in the budding described above.
- Secondly, there is the evidence from the development, namely, the presence of the entocodon in the medusa-bud, a structure which, as explained above, can only be accounted for satisfactorily by derivation from a medusan type of organization.
- Woltereck , on the other hand, have shown that the ectodermal pit which gives rise to the pneumatophore represents an entocodon.Advertisement
- Hence the entocodon represents a precocious formation of the sub-umbral surface, equivalent to the peristome of the polyp, differentiated in the bud prior to other portions of the organism which must be regarded as antecedent to it in phylogeny.