RESUMO
Unfertilized eggs of sea urchins, Hemicentrotus pulcherrimus and Pseudocentrotus depressus, were treated with 4-5% butyric acid-sea water for 40-60 sec so that they were activated partheno-genetically without visible cortical changes. When these insufficiently activated eggs were inseminated 90-120 min after butyric acid-treatment, they divided much earlier than the control eggs in the first cleavage cycle. In the present paper, it becomes clear that if eggs are put into m/2,000-m/16,000 DNP-sea water at 60 min after insufficient activation and 30 min later, returned to normal sea water and then inseminated, they still show acceleration of the first cleavage in the same degree as the eggs which are not treated with DNP, while if eggs are exposed to DNP for 30 min prior to the insufficient activation or within 60 min after the activation, they do not show any acceleration of the cleavage. From these results, it may be concluded that some preparations for cleavage acceleration which are arrested by DNP become ready in the eggs at an early period in the first cleavage cycle and these preparations cannot be cancelled by DNP-treatment once they have been completed.
RESUMO
Unfertilized eggs of sea urchins were treated with benzimidazole. They were fertilized after being kept in normal sea water for a certain period. It was found that the first cleavage occurred much earlier than in the control. The eggs had a tendency to cleave directly into 3 or 4 cells. Benzimidazole induced some visible changes in unfertilized eggs, which was considered to be the result of an insufficient activation. Benzimidazole was found to have the same effect as hypertonic solution has in Loeb's "double treatment" method for artificial parthenogenesis. When eggs activated with butyric acid were treated with benzimidazole instead of hypertonic solution, they cleaved in a high percentage.
RESUMO
In the area between the equatorial and the upper vegetal regions of the egg of the newt, Cynops (Triturus) phrrhogaster, strips of cellophane, ordinary filter paper or Millipore filter respectively were inserted transversely at short distances ahead of the advancing cleavage furrow. When a cellophane strip is inserted across the future path of the furrow at 0.5-0.7 mm beyond the furrow tip, the furrow stops on reaching the position of the inserted cellophane strip. If, however, a strip of the Millipore filter is inserted at the same distances ahead of the cleavage furrow, the furrow reaches the one side of the Millipore filter strip and soon appears on the opposite side of it, just as the furrow jumps across the strip, to continue the previous course. Similar tendency is observed in the experiments on insertion of strips of the ordinary filter paper. It is suggested that certain propagating factors which are necessary to induce formation of the cleavage furrow can go through the pores of the Millipore filter to precede the advancing tip of the cleavage furrow.
