2QO CARL R. MOORE. 



not assert any capacity for the initiation of development: how- 

 ever if the eggs were subsequently exposed to the proper treat- 

 ment with hypertonic sea-water a goodly per cent, will develop 

 to swimming plutei. The non-fertilizable condition is not due 

 to the death of the egg but to a changed physiological condition 

 induced by the initiatory action of the butyric acid treatment. 

 Whatever the changes brought about, all of the conditions 

 mentioned above are accompanied by the loss of substances 

 from the egg, if indeed the condition is not a result of the loss of 

 some substance or substances that are necessary for fertilization. 

 This loss may be due either to the escape from the egg of the 

 necessary substance or to new chemical combinations within the 

 egg made possible by the disturbance of its physiological equi- 

 librium. 



It is highly interesting to note that a qualitative and possibly a 

 quantitative test for one substance at least has been discovered 

 by F. R. Lillie. This substance fertilizin is continually liberated 

 ,from the egg into the surrounding sea-water as long as it remains 

 in a fertilizable condition and as pointed out on page 276 it has 

 been found to afford an absolute test (using a fresh sperm suspen- 

 sion as an indicator) of the capacity of sea-urchin eggs for 

 fertilization in seven analyzed cases and will probably be found 

 to hold for all cases in Arbacia, as it is evidently an indicator of 

 a generalized condition. 



An analogous condition to that in Arbacia, of the loss of 

 substances from the egg and the consequent lack of capacity 

 for fertilization, has been found in other forms than the sea- 

 urchin, though in no other forms than Arbacia and Nereis has a 

 qualitative test for a substance been found. E. E. Just ('15) 

 has discovered that if eggs from Platynereis are collected in sea- 

 water they cannot be fertilized. This is due to some effect of 

 the sea-water in causing the loss of necessary substances for 

 fertilization either through diffusion from the egg or through 

 new chemical combinations within the egg. If only a few drops 

 of sea-water come in contact with the egg they will not fertilize 

 despite the fact that sperm penetrate the eggs and produce weak 

 changes characteristic of fertilization : the proper egg substances 

 for the intiatory reactions are not available. 



