ECHINODERMATA 139 



Echlnoderm eggs are especially convenient for studies on the 

 physiological changes occurring during development. Warburg 

 found for example that fertilized starfish eggs utilized oxygen eight 

 times as fast as the unfertilized ones. Important studies on the 

 changes in permeability of eggs immediately following fertilization 

 have been made by R. Lillie and more recently by Dorothy Stewart. 



F. Lillie and E. Just believe that the secretions of Arbacia (a sea 

 urchin) eggs contain an amboceptor with an ovo-phile side chain 

 which combines with the egg and a spermo-phile side chain which 

 combines with the sperm. The egg secretion enables the sperm 

 to fertilize the egg. (Consult Lillie, F. R. 191 9. Problems of 

 Fertilization. Univ. of Chicago Press.) 



But A. E. Woodward finds that it is possible to precipitate from 

 the egg secretion by one method a substance which activates the 

 sperm, and by another method a second substance which brings 

 about parthenogenetic development of the sea urchin egg. Dr. 

 Woodward has also utilized iodin (see page 439) as an agent in 

 parthenogenesis. (Consult Woodward, A. E., and Hague, F. S. 

 1917. Iodine as a parthenogenetic agent. Biol. Bull., vol. 38, 

 PP- 355-360.) 



The writer of this text believes that iodin saturates the un- 

 saturated fats of the egg, and that increased oxidation causes cell 

 division to occur.^ (See papers by Chidester and associates.) 



Parental Care. — In the Asteroidea, the young are sheltered in 

 the arms of the adults. One form, Pteraster, has a tent-like brood 

 pouch. 



Regeneration. — The Echinoderms have a well-developed charac- 

 teristic known as self-mutilation or autotomy. This is most marked 

 in many Ophiuroids, some Asteroids and some Holothurians, but 

 does not occur at all among the Echinoids. Brittle-stars and star- 

 fishes, when removed from water or molested, will sometimes break 

 off portions of their arms, piece by piece, to the very base. The 

 central disc is entirely capable of regenerating new arms. The sea 

 cucumbers frequently eviscerate themselves, escape from their 



2 Iodin has a well-known corrosive action on fats, and it is undoubtedly effective 

 m dissolving the fatty pellicle around tubercle bacilli as well as other pathogenic 

 organisms treated successfully by cod liver oil. The West Virginia University group 

 are treating certain diseases with super-iodized cod Hver oil. Possibly iodin is re- 

 sponsible for the protective and curative actions ascribed to other chemicals admin- 

 istered in combination with it. 



