Manchester Memoirs, Vol. Ixii. (191 7), No. 2 33 



These salts, however, were not equal in regard to their power of 

 action, thus, Cl<Br<rNO. ? <CNS<I. This loss of pigment was 

 taken to indicate that the surface permeability had been affected 

 by the salts. Further, if the eggs were treated with the above 

 solutions for varying periods, according to the salts used, and 

 then transferred to normal sea-water development commenced 

 and larvae were produced. Experiments with the eggs of Asterias 

 showed that the weakly acid salts, such as chloride and bromide, 

 were better agents than the stronger ones. This is in direct 

 opposition to the result obtained with Arbacia eggs, -and would 

 seem to indicate that the egg membrante of the starfish ^was 

 thinner than that of the sea urchin. 



As a further test whether the conception of changed perme- 

 ability for inducing parthenogenesis was correct, a second series 

 of experiments were undertaken. Calcium chloride was known 

 to retard increase in permeability and it was therefore decided 

 to ascertain the effect of a mixture of this substance and those 

 that produced development. 



Some eggs of Arbacia were treated as described above, while 

 others were placed in the same solution to which small quanti- 

 ties of calcium or magnesium chloride were added. This latter 

 solution prevented membrane formation and cell cleavage, while 

 the control eggs developed into larvse. 



Fertilisation then brings about altered conditions of inter- 

 change of diffusible substances and ions; thus before fertilisation 

 the cell membrane is only partially permeable to anions, but 

 after fertilisation the permeability to these ions is greatly in- 

 creased. The original chemical equilibrium is thus disturbed, with 

 the result that the cell metabolism is affected in such a way as to 

 cause development. Lyon found that during cell cleavage the 

 production of C0 2 is not constant, but is rhythmical, the rhythm 

 corresponding to the cleavage. This rhythm, according to Lillie, 

 corresponds to periods of increased and decreased permeability. 

 However, in artificial parthenogenesis the increased permeability 

 must not be allowed to continue indefinitely, but must, after a 

 certain period, be stopped by the use of a hypertonic solution, 

 or some other agent producing the same effect, such as cold or 

 lack of oxygen. 



In a recent paper (191 6) Gray has confirmed many of Lillie 's 

 results and demonstrated that after normal fertilisation there is a 

 marked decrease in electrical resistance, and that for the first 

 hour of development the resistance never returns to the same 

 value as it had before fertilisation occurred. In a series oY ex- 



