Artificial PartJirnogenesis in Starfish Eggs 389 



of the first polar body; still, no such well-defined periodicity was 

 found as with the experiments on the effects of warming (pp. 396, 

 et seq.) The appearances indicate a difference in the conditions 

 of the membrane-forming process — the acid acting by a simple 

 lipolytic action on the surface layer, while the effect of heating 

 depends on acceleration of an enzyme action, as already suggested. 

 Variations in the quantity or in the condition of the enzyme would 

 affect the results of warming without altering those due to the 

 simple action of a fat solvent. 



Later I shall give some further observations on membrane- 

 formation in starfish eggs. The process certainly seems to be 

 correlated with a change in the developmental capabilities of the 

 egg. It does not however necessarily lead to an acceleration of 

 the oxidations in the egg, as is shown by the fact that immature 

 eggs in which membranes have been formed show no increased 

 disposition to undergo the typical oxidative coagulation or cyto- 

 lysis (p. 408); yet under certain conditions (after maturation has 

 begun) such an accelerated oxidation does seem to result and to 

 constitute an important condition of development, as already 

 indicated. The experiments to be described later show, however, 

 that only a small part of the effects of momentary warming can 

 thus be accounted for. In the starfish egg, in fact, repression 

 rather than acceleration of oxidations seems to be an important 

 condition of the initiation of the developmental process, although 

 this latter once begun naturally requires free oxygen for its con- 

 tinuance (p. 413, et seq.) 



B Development of Eggs after Momentary Warming 



Membrane-formation is followed after a more or less prolonged 

 interval by a series of form-changes in the egg; these under favor- 

 able conditions take the form of regular cleavage. It must be 

 regarded as significant that the most manifold and irregular 

 changes of form may occur, with all gradations between the pro- 

 trusion of pseudopodia and the assumption of various irregular 

 uncleaved forms or the production of irregular and unequal cleav- 

 ages and fragmentations on the one hand, and the normal process 



