SOME NOTES ON THE FERTILIZATION REACTION 

 IN ECHINODERM EGGS. 



LIBBIE H. HYMAN, 

 HULL ZOOLOGICAL LABORATORY, UNIVERSITY OF CHICAGO. 



The following observations make no claim to novelty but are 

 perhaps worthy of record as additional evidence on certain 

 matters. They are concerned solely with the fertilization re- 

 action, that is to say, with the activation of the egg, and not with 

 cleavage. Activation and cleavage must, I think, be regarded 

 as distinct processes. 



The observations were made in May, 1922, at the Hopkins 

 Marine Station, Pacific Grove, California. I am indebted to 

 the director, Dr. W. K. Fisher, for the privilege of working at 

 the station and for his unfailing promptness in supplying me 

 with everything necessary for my work. 



I. Materials and Methods. The eggs used were those of the 

 Pacific coast sea-urchins, Strongylocentrotus franciscanus and 

 purpuratus, and of the starfish, Patiria miniata. The latter is 

 the Asterina of Loeb. The eggs of the urchins were obtained by 

 removing the oral portion of the test, leaving the ovaries in the 

 aboral portion. All other viscera and tissues were then removed 

 from the latter and it was rinsed several times with sea-water. 

 Upon standing for a short time, those portions of the ovaries 

 which are ripe break down, releasing the eggs, which may then 

 be removed with a pipette. The urchins were evidently past 

 their prime at the time during which I worked with them as 

 only small portions of the ovaries contained mature eggs. These 

 seemed, however, to be entirely normal in most cases, and gave 

 a high percentage of fertilization membranes and cleavage. 



The eggs of Patiria employed were normally shed eggs. It 

 was found that when these starfish are spread out on a table, 

 a considerable number of them (presumably those that happen 

 to be ripe) will begin to shed eggs and sperm and continue this 

 for three or four hours. It may be noted in passing that the nor- 

 mally shed eggs of Patiria are fully mature, are immediately 



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