V] 



OF THE SPERM-CELLS OF DECAPODS 



441 



by various salts in their respective concentrations, a similarly 

 identical effect is produced when these concentrations are doubled 

 or otherwise proportionately changed. 



KNO 



Fig. 147. Sperm-cells oi Inachtis, as they appear in saline solutions of 

 varying density. After KoltzoflF. 



Thus the following table shews the percentage concentrations of 

 certain salts necessary to bring the cell into the forms a and c 

 of Fig. 147; in each case the quantities are proportional to the 

 molecular weights, and in each case twice the quantity is necessary 

 to produce the effect of c, compared with that which gives rise to 

 the all but spherical form of a. 



% concentration of salts in which 



the sperm- cell of Inachus 



assumes the form of 



If we look then upon the spherical form of this cell as its true 

 condition of symmetry and of equiUbrium, we see that what we 

 call its normal appearance is just one of many intermediate phases 

 of shrinkage, brought about by the abstraction of fluid from its 

 interior as the result of an osmotic pressure greater outside than 

 inside the cell, and where the shrinkage of volume is not kept pace 

 with by a contraction of the surface-area. In the case of the blood - 

 corpuscle, the shrinkage is of no great amount, and the resulting 

 deformation is symmetrical; such structural inequahty as may be 

 necessary to account for it need be but small. But in the case of 

 the sperm-cells, we must have, and we actually do find, a somewhat 



