. Biological structure and function; proceedings. Biochemistry; Cytology. 502 T. GUSTAFSON time-space pattern. As an example we may study the release of the pulsatory activity. This activity starts in zone i and brings about a release of the primary mesen- chyme cells into the blastocoel; continues in zone 2 where it brings about the primary invagination of the archenteron rudiment; continues in zone 3 where it brings about an early evagination of the coelomic sacs; continues in zone 4 where it may contribute to the morphogenesis (a rounding up) of the oesophagus; continues (occasionally) in z
. Biological structure and function; proceedings. Biochemistry; Cytology. 502 T. GUSTAFSON time-space pattern. As an example we may study the release of the pulsatory activity. This activity starts in zone i and brings about a release of the primary mesen- chyme cells into the blastocoel; continues in zone 2 where it brings about the primary invagination of the archenteron rudiment; continues in zone 3 where it brings about an early evagination of the coelomic sacs; continues in zone 4 where it may contribute to the morphogenesis (a rounding up) of the oesophagus; continues (occasionally) in zone Fig. 4. The bending of the archenteron towards the presumptne stumodaeum. a shows how contact has been formed between the archenteron tip and the ventral side by means of pseudopods. The tension in the pseudopods has caused the formation of cones of attachment in the ectoderm and pulled out cells from the archenteron tip, the whole of which will gradually (through the pull of several pseudopods of this kind) be forced to make contact with the ventral side. In b the contact has been established. The archenteron tip is sometimes met by the invaginating stomodaeum rudiment, an invagination which recalls the primary invagination of the archenteron. The pulsatory activity in the other zones generally fails, with some exceptions. It may thus occur (preliminary studies) in the ectoderm where it mav contribute to the invagination of the presumptive stomodaeum [2]. It also occurs in the regions between the extending arms and thus con- tributes to their elongation [4]. The difference in the morphogenetic activity of the consecutive zones is not onlv a time difference. There also appears to be a decrease in the capability of the cells to pulsate and to emit pseudopods and an increase. 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 may not perfectly resembl
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Keywords: ., bookcentury1900, bookcollectionbiodiver, booksubjectbiochemistry
