EEPEODUCTION OF CELLS. 155 



not be created.* Life is potential, — that is, endowed with 

 energy. Its every manifestation proceeds from the utilization 

 of force. Inheritance is but an expression of a local fact, 

 included in the phrase persistence or correlation, conservation 

 or convertibility of force. It can, therefore, be studied in its 

 relations to law. 



Like produces like in the cell ; for we have in the new cell 

 but another expression of the parent cell, brought about from 

 and through the transference of force. As every force acting 

 on a cell must produce some effect (for cause and effect are 

 correlative, of necessity), we needs have changes produced 

 through environment, and the cell in which these changes are 

 produced cannot be the same cell as it was previous to such 

 changes, and can, in the line of transference of force, but 

 reproduce itself as it is. There must needs be, then, in the 

 cell a series of reproductions, in order to gain development. 

 As another sequitur, we have limits to the power for repro- 

 duction, for work can only be performed by the use of energy, 

 and each change in a cell is an expression of work performed 

 or energy used ; and when the changes demanded by environ- 

 ment are too great for the remaining forces of the cell, and 

 new forces cannot be assimilated from elsewhere, there must 

 be a cessation of reproduction, and in time a destruction of 

 form. 



THE SPERM. 



In considering the cell, we remarked upon the functions of 

 the nucleus as tending rather to the maintenance and multi- 

 plication of the cell, than to its specific office. In the sperm 

 we shall have occasion to again refer to this important prov- 

 ince of the nucleus. 



The semen — or the contribution of the male animal towards 

 the generation of offspring — consists essentially of the sper- 

 matozoa. Besides this, the product of the testicle, the 

 ejected fluid contains the secretions of other glands, which 

 probably serve the purposes of dilution for the fluid in which 

 the spermatozoa move. Certain it is, from the beautiful 

 experiments of Mr. Newport, that impregnation does not take 

 place until the spermatozoon actually comes in contact with 

 the ovum, and penetrates within its substance. 



* That is, formed from nothing, — an inconceivable proposition. 



