May 31, 1895.] 



SCIENCE. 



t)03 



■ Tendencies ' and • proclivities ' are words 

 that have no legitimate place in the discus- 

 sion of the data of biologj- any more than 

 they have in natural philosophy or physics. 

 Karyokinesis, now admittedly inseparable 

 in thought from the idea of multicellular 

 development, is a rliythmical process so 

 complex in its d_^^lamical aspects as to some 

 extent lead one unwittingly to underesti- 

 mate the absolute continuity of the accom- 

 panying processes of metabolism. But that 

 is no reason why the importance of nuclear 

 metamorphosis should be exaggerated at 

 the expense of the far more important 

 forces developed by metabolism and gi-owth. 

 In fact, the ' ids,' ■ idants,' etc., of that 

 school of biologists are not causes but mere 

 etl'ects, produced as passing shadows, so to 

 speak, in the operation of the perfectly con- 

 tinuous processes of metabolism incident to 

 development. Keciprocal relations are sus- 

 tained between nucleus and cytoplasm of 

 such importance that the transformation or 

 fission of the one is impossible without the 

 other. 



The so-called 'reducing divisions' probably 

 have nothing but a passing and purely adap- 

 tive physiological significance in every on- 

 togeny of ova and sperms. The far-fetched 

 and extraordinary teleological significance 

 given by some to the reducing divisions 

 would lead one to suppose that the clairvoy- 

 ant wisdom of the original egg that thus 

 first threw out the excess of its ancestral 

 ' germ-plasm ' in order to save its posterity 

 from harm through the fatality of reversion 

 thus entailed was greater than anj'thing 

 human, if not god-like. The complete par- 

 allelism of the ' reducing division ' in the 

 sperm and egg has never been established. 

 Tlie comparison of these processes in the 

 two is still only approximate, because in 

 the truly hololilastic egg thei-e is. in some 

 cases, an api)arent temporarj' substitution 

 of the male nucleus for the female, as is 

 shown by the former's a.ssuming a position 



of equilibrium at the cinter of the ovum 

 (Ascaris), a condition of things that does 

 not and could not occur in the sperm cell. 



A still more important contrast is the al- 

 most incredible difference of volume of the 

 two kinds of sex-cells of the same species. 

 In man the ratio of volume of the male cell to 

 the female cell is as 1 to 3,000 approximately. 

 This extreme contrast of volume is asso- 

 ciated with corresponding contrasts in their 

 properties. There can hardlj- be any doubt 

 that the mature male cell is in a nearly po- 

 tential or static state of metabolic transfor- 

 mation of its substance, and is characterized 

 by an almost complete want of stored meta- 

 bolizable reserve material. The egg is in a 

 similar static state, but. on the other hand, 

 contrasts with the male element in that the 

 development of a more or less voluminous 

 mass of resei've material within it has 

 seemingly been also associated with its loss, 

 as a rule, of the power to begin an inde- 

 pendent development. The power of the 

 male cell to begin its transformation and 

 growth through metabolism appears to be 

 arrested until it finds the material in which 

 its mere presence will set up transforma- 

 tions. This it must do by in some way set- 

 ting free and diflusing some of its own mole- 

 cules osmotically and mechanically through 

 the egg. The substance of the egg appears 

 therefore to be complementary to that of 

 the spermatozoon. The power to set up 

 transformations within the egg leading to 

 the development of a new being is not 

 manifested aside from the presence of the 

 male element except in cases of partheno- 

 genesis. Even the expulsion of the polar 

 cells is not initiated until the stimulus of 

 the presence of the male element is experi- 

 enced bj- the egg. 



Another contrast is found in the times of 

 the advent of the ' reducing division' in the 

 two kinds of sex-cells. In the male cell 

 the ' reducing division' occurs earliest, or 

 while it is still in more or less close nutri- 



