ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 329 



Appearance of Division Spindle in Sea-urchin Ova. — ;L. V. 

 Heilbrunn (Journ. Exper. Zool, 1920, 30, 211-37). During the 

 period between fertilization and the first cleavage of the sea-urchin egg 

 the viscosity of the cytoplasm rises until it reaches a maximum, then it 

 decreases again. Similar changes occur in relation to the second cleavage. 

 The changes in viscosity are very marked. and indicate the occurrence of 

 a gelation in the cytoplasm. This reaches its height just before the 

 spindle appears ; later on the cytoplasm becomes more fluid again. The 

 gelation is a predetermining factor in spindle or aster formation : if 

 it is suppressed the mitotic figure does not form. Such suppression can 

 be produced by fourteen different substances, all lipoid solvents ; it can 

 also be produced by cold. Although effecting the same result, the 

 actions of cold and of lipoid solvents are mutually antagonistic. The 

 effect of hypertonic solutions on dividing eggs may be interpreted as 

 due to an increase of the cytoplasmic viscosity. Potassium cyanide and 

 chloretone also act in this way. The cytoplasmic gelation which occurs 

 in relation to mitosis is apparently due to an abstraction of water, for it 

 ■can be most closely imitated by an abstraction of water, and entrance of 

 water into the fertilized esfg reverses the normal cytoplasmic gelation. 



J. A. T. 



Complete and Functional Hermaphroditism in a Sea Urchin. — 

 Maurice Herlant (Arch. Zool. Exper., 1918, 57, Notes et Revue, 

 28-31, 1 fig.). In Paracentrotus lividus hermaphroditism was observed, 





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m 





Section of hermaphrodite gonad showing large oogonia 

 and numerous minute sperm-cells. 



a very rare occurrence. It has been noted by Yiguier in Sphser echinus 

 granular is. The specimen showed three normal testes, an atrophied 

 testis, and a mixed gonad with both ova and spermatozoa. Autogamy 

 was effected artificially, and could no doubt occur in nature. Accidental 

 hermaphroditism has been recorded in Asterias glacialis. In Asterina 

 gihbosa it is known that the young individuals are males and become 

 female. Giard has described a similar condition in Echinocardium 

 ■cordatum. J. A. T. 



