270 CARL R. MOORE. 



obtained after the same exposure to the weaker solution. But a 

 comparatively short exposure (5 to 10 min.) to the stronger 

 concentration results in the production of quite a considerable 

 number of membranes. The membranes too are decidedly 

 more pronounced than those produced after exposure to the 

 weaker solution but are not yet like the fertilization membrane 

 produced in normal fertilization, even though the physiological 

 processes responsible for their production may be analogous' 

 except perhaps in intensity. Cleavage, after this exposure, 

 although departing very greatly from the normal, is not char- 

 acterized, as are many of them after the weaker solution, by the 

 separation of the blastomeres; the cells remain in close proximity 

 to each other a fact that may possibly be associated with the 

 more rigid membrane that is produced around the egg and a 

 larger percentage of them reach the swimming stage than of 

 those from the other solution. But here also as the length of 

 exposure is increased and the curve of cleavage falls, the same 

 decline in degree of normality and of percentage of swimming 

 larvae is apparent. 



In keeping with the more pronounced effect of the stronger 

 solution in the production of membranes is the fact that the 

 eggs suffer a greater increase in permeability. Loss of pigment 

 is more pronounced than in the case of the weaker solution as 

 one would expect. A small percentage of swimming larvae 

 obtained after a relatively short exposure to the stronger solution 

 are somewhat normal, but the lots grade so gradually into ab- 

 normality and immobility that many can be seen to possess 

 but very little power of movement. Many half, quarter or 

 eighth sized larva? are found here, as well as following an exposure 

 to the weaker concentration. 



There is revealed here a general shake-up of development 

 that is quite characteristic, not merely for the hypertonic treat- 

 ment, but for development after treatment with any agent that 

 tends to destroy the delicate physico-chemical balance of an 



egg- 



This experiment which may be considered a typical one, 

 offers no indication that the addition of a sperm suspension to 

 eggs that have been activated by hypertonic sea-water are yet 



