T H E E A R L Y E M B R Y O G E N E S I S OF I N S E C T S
283
were dependent upon a factor region near the posterior pole including
the oosome before its dissolution, Bier supposes the particle migration to
be homologous to the influence of the activation centre in Platycnemis.
Analysis of the different activation processes constituting the reaction
sequence is as yet only in its initial stages. This discussion, therefore, can
be based only on a chain of inferences from experiments on different
objects. Considering the nature of the changes taking place in the endoplasm under the influence of the AC, we may tentatively postulate three
categories: transport or migration of particles, biochemical processes,
and rearrangement of macromolecules for instance into fibrils. All these
changes may be dependent on the nuclei in energids and vitellophags.
Apart from the transport of materials effected by migrating cleavage
energids, the increase in primary periplasm and the reinforcement of the
germ anlagen blastoderm with secondary periplasm are the most striking particle movements in the early insect egg. Aggregation of the
secondary periplasm is more likely governed by the yolk plasmodium
than by the blastoderm, since in Apis ligation does not cause a distinct
shift of the secondary periplasm maximum comparable to that of blastoderm cell density (Schnetter, 1936). Of the metabolic processes observed
so far, breakdown of yolk bodies at first is of no general importance;
however, the endoplasm, especially underneath the germ anläge, may be
'liquefied' (Apis, Tenebrio) so as to facilitate movements of this blastema. As for contractility of the yolk plasmodium, e.g., in Gryllus or
Platycnemis, production and parallel arrangement of contractile protein
molecules must be important. So far, however, neither intracellular
fibrils nor contraction releasers like ATP have been found.
B. Autonomous Ooplasmic Processes
Visible changes of ooplasm as described above (Section V A) must be
due to 'substanz wechserphysiologische' (Seidel, 1952) or 'physiodynamische' (Lehmann, 1958) phenomena which are not themselves observable but could be analysed by modern submicroscopical or biochemical
methods. Despite some pioneer work (Okada and Waddington, 1959),
very little is known about the changing substructure of insect ooplasm,
yet we may draw some conclusions as to the place, time, and possible
type of such changes in order to point out some directions for further
research. In this connection, we may ask which developmental processes
occur autonomously in the ooplasm, that is, in the absence of the genome,
and which processes, on the other hand, depend upon nucleo-cytoplasmic interaction.
Clear examples of autonomous ooplasmic processes are provided by
Camponotus and Gryllus. In the egg of Camponotus, the thin and evenly
distributed periplasm differentiates during cleavage into several areas
283
were dependent upon a factor region near the posterior pole including
the oosome before its dissolution, Bier supposes the particle migration to
be homologous to the influence of the activation centre in Platycnemis.
Analysis of the different activation processes constituting the reaction
sequence is as yet only in its initial stages. This discussion, therefore, can
be based only on a chain of inferences from experiments on different
objects. Considering the nature of the changes taking place in the endoplasm under the influence of the AC, we may tentatively postulate three
categories: transport or migration of particles, biochemical processes,
and rearrangement of macromolecules for instance into fibrils. All these
changes may be dependent on the nuclei in energids and vitellophags.
Apart from the transport of materials effected by migrating cleavage
energids, the increase in primary periplasm and the reinforcement of the
germ anlagen blastoderm with secondary periplasm are the most striking particle movements in the early insect egg. Aggregation of the
secondary periplasm is more likely governed by the yolk plasmodium
than by the blastoderm, since in Apis ligation does not cause a distinct
shift of the secondary periplasm maximum comparable to that of blastoderm cell density (Schnetter, 1936). Of the metabolic processes observed
so far, breakdown of yolk bodies at first is of no general importance;
however, the endoplasm, especially underneath the germ anläge, may be
'liquefied' (Apis, Tenebrio) so as to facilitate movements of this blastema. As for contractility of the yolk plasmodium, e.g., in Gryllus or
Platycnemis, production and parallel arrangement of contractile protein
molecules must be important. So far, however, neither intracellular
fibrils nor contraction releasers like ATP have been found.
B. Autonomous Ooplasmic Processes
Visible changes of ooplasm as described above (Section V A) must be
due to 'substanz wechserphysiologische' (Seidel, 1952) or 'physiodynamische' (Lehmann, 1958) phenomena which are not themselves observable but could be analysed by modern submicroscopical or biochemical
methods. Despite some pioneer work (Okada and Waddington, 1959),
very little is known about the changing substructure of insect ooplasm,
yet we may draw some conclusions as to the place, time, and possible
type of such changes in order to point out some directions for further
research. In this connection, we may ask which developmental processes
occur autonomously in the ooplasm, that is, in the absence of the genome,
and which processes, on the other hand, depend upon nucleo-cytoplasmic interaction.
Clear examples of autonomous ooplasmic processes are provided by
Camponotus and Gryllus. In the egg of Camponotus, the thin and evenly
distributed periplasm differentiates during cleavage into several areas