146 



MORPHOLOGY OF FERTILIZATION 



finned in living material in other species of starfish and in the 

 holothurians, Holothiiria atra and Thijone briareus (Colwin and 

 Colwin, 1955a,c, 1956). Quantitative data for the acrosome 

 reaction have been obtained in Thy one. 



Table I. Acrosome Reaction of Spermatozoa of Thjjone briareus as Obseived 



in Living Preparations. Production of Acrosome Filaments Evoked by Adding 



Sea Water Sperm Suspensions to Egg Water or to Sea Water Made Alkaline 



by Addition of O.liV NH4OH. (From Colwin and Colwin, 1956.) 



Note. Experiments bearing the same number were made simultaneously 

 from the same sperm suspension and have the same control. 



°E eggs; S sperm; N naturalh' shed; G obtained b^' removal from 

 gonad. 



^ Sweep Extensive examination of area of coverslip by back and forth move- 

 ment with a mechanical stage. 



' pH of alkaline sea water to which sperm suspension was added was slight) v 

 higher than 9.2-9.4 



■^ pH of alkaline sea water to which sperm suspension was added was 9.2-9.4. 



Thyone briareus. In this species acrosome filaments were 

 formed when sperm suspensions were treated either with egg 

 water or with alkaline (ammoniated) sea water (Table I). 

 Within the concentrations used, the latter was found to be the 



