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A Note on the Effect of Acid, Alkali, and certain Indicators in 

 Arresting or otherwise Influencing the Development of the 

 ■Eggs of Pleuronectes platessa and Echinus esculentus. 

 By Edward "Whitley, M.A. (Oxon.). 



(Communicated by Professor W. A. Herdman, F.R.S. Received November 14, 

 —Read November 23, 1905.) 



I. Effect of Acid and Alkali on the Eggs of Pleuronectes. 



While working last spring at the Port Erin Biological Station on the 

 effect of acids and alkalies upon the development of Echinus eggs, it was 

 suggested to me that it might be interesting to try the general effect of 

 similar solutions upon some other type of organism. 



For this purpose the eggs of the Plaice (Pleuronectes platessa) were selected, 

 as they were to be obtained in abundance from the fish-hatchery attached to 

 the station, but, as time pressed, it was only found possible to experiment 

 with one acid and one alkali, and decinormal solutions of hydrochloric acid 

 and sodium hydrate were accordingly used. 



In a pond attached to the hatchery numbers of plaice are kept in the 

 spawning season, and the surface of the pond is skimmed each morning for 

 the purpose of collecting the eggs, which are then placed in the hatching 

 apparatus. Three batches of these eggs of different ages were taken for 

 experimentation — those freshly skimmed from the pond, those which had 

 been removed two days before and had remained since in the hatching 

 apparatus, and those taken 10 days before and similarly treated. Some few 

 eggs always escape the net in the process of skimming, and are taken in the 

 catch of later days, so that, when 10 days old eggs, for instance, are spoken of, 

 what is meant is that none can be younger than that, although some few may 

 be slightly older. Such as showed obvious differences in age from the 

 majority of each batch were removed. 



The eggs were treated in a similar way to that employed in a research 

 carried out at the same time on Echinus eggs,* namely, they were placed in 

 small batches in a number of tumblers, each containing 200 c.c. of sea- 

 water, to which measured amounts of the decinormal solutions of acid or 

 alkali were added. A summary of previous work on the effects of acid and 

 alkaline solutions upon development will be found in the paper above 

 referred to. 



* See preceding paper. 



