PARTHENOGENETIC MEROGONY OR DEVELOPMENT WITHOUT NUCLEI OF THE EGGS OF SEA URCHINS FROM NAPLES

Abstract

The non-nucleate parts of the eggs of Arbacia pustulosa, Sphaerechinus granularis, Parechinus microtuberculatus and Paracentrotus lividus, obtained by centrifugal force, can be artificially activated. They throw off fertilization membranes characteristic of the sp., form asters and begin to develop. Development of the parthenogenetic merogones of A. pustulosa is similar to that of A. punctulata, previously descr. The parthenogenetic merogones of Parechinus and Paracentrotus develop by a process of progressive fragmentation inside the fertilization membrane, similar to that observed in the parthenogenetic normal egg which leads to normal free-swimming blastulae. No further development of eggs without nuclei has been obtained beyond the blastula. Cleavage may take place in whole eggs while the nucleus is still intact. Certain changes take place in immature eggs when treated with parthenogenetic agents similar to those of the mature egg.