390 E - E - JUST. 



observation on the egg of Strongyloccntrotus. Using concentrated 

 solutions (2 l / 2 and i l / 2 n NaCl and 2^2 n and 2 n cane sugar), 

 Loeb 1 found that the unfertilized eggs of 5". purpuratns form mem- 

 branes in the same way as in fertilization. The details of his 

 description differ very little from those I have given above for 

 the egg of Arbacia. 



Moore, working with Arbacia, was able by the use of hypertonic 

 sea-water alone (16 c.c. 2 J / 2 M NaCl plus 50 c.c. sea-water) to 

 obtain " quite a considerable number of membranes." According 

 to Moore, however, these membranes are not like the fertilization 

 membranes produced in normal fertilization. 



In those lots of eggs that show a high per cent, of immature 

 eggs, some mature eggs may fail to show membrane separation in 

 any concentration of hypertonic sea-water. Stale eggs often fail 

 to respond to hypertonic solution with membrane separation. 

 Blood inhibits membrane separation and enhances the cortical 

 changes that give the thick swollen cortex. Eggs that fail to form 

 membranes in the hypertonic sea-water are invariably from lots 

 that yield a low per cent, of membranes following normal insemi- 

 nation. We may consider these points in detail. 



On June 29, July 8, July 18, for example, uninseminated eggs 

 were mixed with blood. In each experiment the eggs were divided 

 into three lots A, B, and C. A was untreated (control), B in- 



,-* 



seminated. and C exposed to hypertonic sea-water. Not a single 

 egg in any of the lots B formed membranes. The lots (C) treated 

 with hypertonic sea-water (20, 22, and 24 parts 2 l / 2 M NaCl plus 

 80, 78, and 76 parts sea-water, respectively) gave a low per cent, 

 of very poor membranes; instead, in the majority the egg cortex 

 became badly swollen. Nothing was more clearly brought out in 

 the work than this sharp inhibition by blood both in fertilization 

 and in experimental parthenogenesis. 



Several experiments, for example, those of August i, 2, and 3, 

 were made on washed eggs. These established that eggs lose 

 their capacity for artificial activation more quickly than their 

 capacity for fertilization. In one case eggs washed but four times 

 in an hour were highly fertilizable, as shown by the presence of 

 96 per cent, membranes and subsequent normal development. 



i Pfliiger's Archiv, '04, 103. 



