744 



SCIENCE. 



[X. S. Vol. XXI. No. 541. 



one to two minutes to 50 c.c. of sea water, to 

 which about 3 or 4 c.c. of n/10 acetic acid 

 had been added, the majority of the eggs 

 formed the membrane characteristic of the en- 

 trance of the spermatozoon. When these eggs 

 were exposed for from thirty to forty minutes 

 to 100 c.c. of sea water to which 14 or 15 c.c. 

 of a 2i n solution of sodiiun chlorid had been 

 added, those of the eggs which had formed 

 membranes developed into swimming larvae 

 that rose to the surface. These larvae devel- 

 oped into perfect plutei as fast as the larvae 

 of eggs fertilized with sperm. When the order 

 of treatment was reversed, not a single larva 

 was formed. When eggs were fertilized with 

 sperm first and then exposed to the hypertonic 

 sea water for from about thirty to forty min- 

 utes, their development became almost iden- 

 tical with that of the unfertilized eggs treated 

 first with acid and then exposed to the hyper- 

 tonic sea water for the same period of time. 



The acid treatment above referred to causes 

 the formation not only of the membrane, but 

 also, in due time, of the karyokinetic spindle. 

 Eggs exposed for only thirty or forty minutes 

 to the hypertonic sea water do not show any 

 changes of any kind. Following the action 

 of the acid, however, treatment with hy- 

 ipertonic sea water appeared to accelerate the 

 mechanism of cell division originated by the 

 acid treatment, and also seemed to increase 

 the vitality or to prolong the life of the egg. 



William J. Gies, 



Secretary. 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON. 



The 599th meeting was held April 1, 1905. 



In a communication made by Mr. K. A. 

 Harris, entitled ' A General Account of the 

 Tides,' brief mention was made of the dis- 

 turbing forces and the ordinary ways of pro- 

 ducing the tide. A small deep body of water 

 may obey the equilibrium theory, i. e., its 

 surface may always be normal to gravity as 

 disturbed by the moon or sun. This theory 

 nearly explains the tides in Lake Superior, 

 the eastern half of the Mediterranean Sea, 

 the southwestern portion of the Gulf of 

 Mexico and of the Caribbean Sea. The ocean 

 tides are due chiefly to stationary waves, or 



oscillations, existing in such portions of the 

 ocean as have for free period approximately 

 the period of the tidal forces. The motion is 

 thus sustained on a considerable scale, just 

 as is the motion of the air particles in a 

 resonator tuned to a sound of constant pitch. 



The principal systems for the semidaily tide 

 were shown on maps, and attention called to 

 the loops and nodes of the oscillating areas. 

 By means of maps of cotidal lines (taken 

 from the Coast Survey Report for 1904) it 

 was shown that over wide areas the tide is 

 nearly simultaneous, while in certain localities 

 the time of tide changes rapidly. In many 

 instances the former regions correspond to 

 loops of the stationary waves, while the latter 

 give indications of nodal lines. Attention 

 was called to isolated points at which there 

 is no rise and fall of tide. Around such 

 points the hours, or times, of the tide run 

 through a complete cycle of values, from 

 to XII. or 0. Such points may be due to the 

 superposition of stationary waves, or to other 

 forms of wave motion; in narrow bodies the 

 deflecting force of the earth's rotation is in- 

 fluential in their production. It was shown 

 that both times and ranges give evidence of 

 the existence and location of these points. 



Mr. John F. Hayford then spoke on ' A 

 Test of Isostasy from Geodetic Observations.' 

 According to the theory of isostasy excesses of 

 mass represented by portions of the earth 

 which are above sea level are compensated for 

 by defects of density beneath them, and simi- 

 larly the density is excessive beneath the 

 oceans. The test referred to is being made 

 in connection with a new computation of the 

 figure of the earth based upon geodetic ob- 

 servations in the United States, which is now 

 in progress in the Coast and Geodetic Survey. 

 The test furnishes a direct proof that the 

 theory of isostasy is true as applied to the 

 northeastern portion of the United States, and 

 also furnishes a determination of the depth of 

 compensation. Charles K. Wead, 



Secretary. 



THE BIOLOGICAL SOCIETY OF WASHINGTON. 



The 399th regular meeting of the Biological 

 Society of Washington was held March 11, 



