1 7 8 



OTTO GLASER. 



Special precautions were taken since the specific gravity read- 

 ings suggested that differences, if at all discoverable by titration, 

 would be small. For this reason the measurements throughout 

 were made with the same burettes and pipettes and comparable 

 titrations always at the same temperature. Moreover it soon be- 

 came apparent that the preparation of the eggs could not be 

 carried out by any of the methods in ordinary practise. I there- 

 fore washed the sea-urchins first very thoroughly in a stream of 

 running fresh water after which they w T ere completely submerged 

 in dishes for from three to five minutes. The bath was followed 

 by partial drying and the complete removal of the spines by means 

 of a coarse cloth. The naked tests were then carefully wiped 

 with a clean towel and placed in an inverted position in individual 

 Syracuse watch crystals. This procedure may appear cumber- 

 some. However, it consumes very little more time than the usual 

 methods of preparation and is the only way in which eggs abso- 

 lutely free from detritus, traces of sea-water, dermal and other 

 secretions, can be gotten. Incidentally the method has a further 

 advantage; the brief immersion in fresh water causes the sea- 

 urchins to shed their sexual products in unusual quantity and 

 with the greatest promptness. Indeed one must work quickly in 



TABLE II. 



