THE DEVELOPMENT OF THE ASCIDIAN EGG CENTRIFUGED BEFORE FERTILIZATION

¹ The Laboratory of Histology and Embryology, College of Medicine, National Central University, China

1. The unfertilized eggs of Ciona intestinalis after centrifuging can be cross-fertilized. The majority undergo cleavage but rarely develop normally.

2. The first cleavage furrow may lie in any plane relative to the position of polar bodies or the axis of centrifuging.

3. In larvae derived from strongly centrifuged eggs, tissues and organs were often displaced from their normal positions.

4. Endoderm and ectoderm appear to be relatively equipotential.

5. There is no evidence that the differentiation of the neural tissue is dependent upon other tissues with which it is in contact.

6. Mitochondria may be displaced from muscle cells and appear in the neural or ectodermal cells, where they are not transformed into myofibrillae.

7. The number of papillae developed by the abnormal larvae varied from none to 3. They are always adjacent to the endoderm which it is suggested may evoke their formation in the ectoderm.

8. The number of sensory pigment spots in the abnormal larvae varies from none to 4. They are always associated with notochordal cells.

9. The organization of unfertilized eggs is found to be strikingly similar to that of fertilized eggs in respect to oöplasmic substances and the capacity of regulation.

10. The elongation of the notochord is not always accompanied by the elongation of the neural plate or tube.