A COMPARISON OF THE DEVELOPMENT OF NUCLEATE AND NON-NUCLEATE EGGS OF ARBACIA PUNCTULATA

¹ From the Marine Biological Laboratory, Woods Hole, and the Biological Laboratory, Princeton University

1. A comparative study has been made for Arbacia punctulata, especially by means of photographs, of the development of the normal whole egg, the white half, the red half fertilized (fertilized merogone) and the red half parthenogenetic (parthenogenetic merogone), all of these both spherical and elongate. The comparative rate of development is also given.

2. Development of the parthenogenetic merogones is not improved by applying various substances to the outside, such as nuclear compounds, hormones and vitamines.

3. A study of the stratification of the centrifuged egg and its halves as seen in prepared sections has been made.

4. Sections of eggs fertilized and then centrifuged show that at a certain stage, the chromatin material is thrown to the centrifugal pole of the nucleus, and that the spindle goes to the centripetal pole intact.

5. Cytological details have been studied, in sections, of the division figure of the normal egg, of the red half fertilized, and of the parthenogenetic merogone. During cleavage stages, the parthenogenetic merogone has well-formed asters, often in pairs, but no spindle and no chromosomes.

6. The Feulgen reaction is negative for the parthenogenetic merogones; there is no chromatin material.

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