Search

1. Regeneration time of the hypostome increases progressively from the oral to the aboral direction. Converse is true for the basal disc. More time is required to form basal disc from aboral-oral direction. 2. In absence of both terminal determinants, the time of regeneration of hypostome and basal disc in a longer piece is less than that of a smaller middle piece; regeneration time in the smaller fragment takes more time. 3. Inhibitory effect of hypostome on the formation of a basal disc has been evidenced in which a slight faster rate of basal disc regeneration is possible in absence of the hypostome in the full length of hydra. 4. In smaller pieces, slower rate of hypostome regeneration is noted in absence of basal disc at posterior regions of the oral end. 5. Hypostome lengthens the time of formation of basal disc in its vicinity, whereas basal disc accelerates the formation of a hypostome in its nearby. Hypostome determining influence is stronger than its counterpart and can act from a greater distance. 6. Determination on hydra has been explained on the basis of an interaction between the relative developmental potential of the participating cells at a given level and the strength of the diffusible communicating system originating from the regions of physiologically active area of hypostome.

1. The cellular configuration of a hydra is dissociated under the pressure of a cover-glass and the different cell types are isolated and observed in hanging drop chamber. 2. With the exception of certain cnidoblasts, all the cells are rounded after dissociation of which only the nutritive muscular cells of the endoderm show amoeboid movement. 3. Pseudopodium originates as ectoplasmic out-pushing in which endoplasm flows in afterwards. Pseudopodia are thrown from all sides of the cell. 4. The details of intra-cellular contents in the different cell-types are described. 5. The nature of surface rigidity, attachment and cell shape before and after dissociation have been discussed in relation to the animal form and morphallactic power of hydra.

Hydra is a unique epigenetic system where simultaneous existence of stability and lability in its cells is encountered. The two terminal ends of the hypostome and basal disc have been designated as unipotentials, in between these two points the area is bipotential, i. e. it can form either basal disc or hypostome.The dynamic state of instability in hydra has been explained on the assumption that in case of a developmental urgency the mid equipotential system can transform into either or both kinds of unipotential through the action of some inhibitory complex.Hypostome as a developmental centre is more powerful than its counter centre namely the basal disc.

1. The progressive effects of temperature fasting on the blastoderms of chick have been studied. 2. The blastoderms do not show any morphogenetic change up to the 7th day of delay prior to incubation. Embryological changes in form of suppression arise in the organisation of blastoderms delayed over 12 days or more. The axes of the embryos tend to be more shortened in the further delayed embryos. 3. The axial structures of the blastoderms suffer reduction in shape and size until they disappear in the blastoderms kept waiting for 15 to 20 days. The blastoderms enlarge into a sheet-like structure without any mark of organisation. 4. The blastoderms become gradually incapacitated beyond the temperature-fasting for over 20 days. 5. The probable mechanism of these morphogenetic features have been sought in the denaturation of "Cell substances" by dehydration, suppression of mitotic activities and morphogenetic movements of cells of the blastoderms.

1. The mitotic peculiarity of the ventricle has been studied. 2. Diffused mitotic activity is noticed throughout the tissue matrix. No definite mitotic zone is seen. The total mitotic activity varies in the different regions as well as in different times of growth. 3. Except in 3 day heart, the rate of cell division is always more in the central area. 4. The ratio of dividing nuclei to resting nuclei in the peripheral region of 3 day heart is higher than that in the central region. 5. The most important item in the individuation of this organ is that the total percentage of dividing nuclei in the different stages, always present a slender figure. However, the cell increase is continuous. 6. The frequency is at its maximum. (11.03%) in 13 day heart, and the minimum (3.09%) in 21 day heart. The percentage of divisional figures in other stages fluctuates in between them. The cell increase in the heart continues even after hatching.