364 E. Newton Harvey 



Chloroform saturated sea-water causes membrane formation 

 in a large per cent of Toxopneustes eggs. If the eggs have been 

 fertilized first, beautiful examples of double membranes can be 

 obtained by after treatment with CHCI3 saturated sea-water/-' 

 The second membrane (due to CHCI3) is just as distinct as the 

 true fertilization membrane and lies halfway between it and the 

 egg surface. These eggs are also more normal looking than unfer- 

 tilized eggs subjected to CHCI3 sea-water treatment as the cytoly- 

 tic changes caused by the CHCI3 do not take place so rapidly on 

 eggs with membranes already formed, probably because the mem- 

 brane offers some resistance to its ready entrance. This second 

 membrane can be formed on eggs which are in the two cell stage 

 and also up to early blastuL-e. 



Inthe two cell stage it is asdistinct asin undivided eggs and sur- 

 round each of the blastomeres. The greater the number of 

 blastomeres the less distinct does it become and the more closely 

 does it surround each cell. The space between it and the cell 

 surface also becomes less transparent as if filled with some other 

 constituents of the blastomeres which have diffused out. The 

 fact that membranes can be produced so late in segmentation 

 stages indicates a considerable similarity in the constitution of 

 the egg during early cleavage stages.^'' 



An extremely fine and delicate second membrane is formed on 

 fertilized Arbacia eggs placed in four times concentrated sea- 

 water as also on the evaporation of the sea-water on a slide. This 

 is accompanied by loss of pigment and other constituents of the 

 eggs. 



Attempts to produce secondary membranes in fertilized Toxop- 

 neustes eggs with CH3COOH failed, even though they were 

 treated long enough to bring about the characteristic effects of 

 over treatment. 



^ Herbst had already performed this experiment. Loc. cit. 



'^On examining the literature I find that Loeb (Arch. Entwm. 23, 1907, p. 479) has already recoided 

 membranes formed on individual blastomeres. In one case 2-4 cell stages were obtained by CaGl2 

 treatment (50 cc. f m CaCl2 +1.6 cc. ^^ NaOH). In another case 2-16 cells were produced by hype"-- 

 tonic treatment. In both cases when sperm was added the individual blastomeres became entirely 

 surrounded by a membrane and dwarf gastrulae resulted from their further development. 



