ARTIFICIAL PARTHENOGENESIS OF ASTERIAS. 167 



process from that observed in the single method. Either agent 

 of the double method may be used alone, and, if given proper 

 exposure, will produce the same effect. The second agent there- 

 fore simply accelerates the activation initiated by the first. There 

 may be all degrees of activation and resultant astral response by 

 either one or both the agents employed. Therefore, Herlant's and 

 Herbst's contentions that in the double method the first activating 

 agent produces a monaster, and the second agent produces a 

 cytaster which unites with the monaster to form either of the 

 polar spindles, is untenable. This contention not only does not 

 agree with observed conditions in Astcrias, but is totally unlike 

 anything occuring in the normal process ; and it has been shown 

 that, following artificial activation, maturation must proceed nor- 

 mally in order that normal development may result. 



CONCLUSIONS. 



1. Maturation in artificially activated eggs of Astcrias may in- 

 volve the extrusion of one, two, or no polar bodies, but only eggs 

 that extrude two polar bodies apparently develop normally. It 

 seems possible that eggs extruding one polar body might develop 

 normally but it has not been demonstrated in this material. 



2. These observations have shown that eggs artificially activated 

 by (i) butyric alone, and (2) butyric acid followed by hypertonic 

 sea-water, are affected similarly in their maturation processes. 

 The second agent in the activation process seems to intensify the 

 stimulus of the first. 



3. Cytasters apparently arise " de novo." 



4. The primary phase of each maturation amphiaster is a mon- 

 aster which arises " de novo " and subsequently divides to form 

 the dicentric figure. 



5. The extrusion of two polar bodies, which has been shown 

 to be the normal method of maturation under artificial activation, 

 results in the presence of a haploid number of chromosomes within 

 the embryo which develop normally. The normal diploid number 

 of chromosomes can only be obtained by the method whereby the 

 second polar body fails to be extruded, which may possibly give 

 rise to normal embryos. 



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