376 H. S. JENNINGS 



The results of the present investigation on the effect of con- 

 jugation need to be considered in connection with the results of 

 the investigations of Calkins, Enriques, Woodruff, and others, 

 on the results of long continued vegetative reproduction. The 

 two lines of work complement each other and lead to harmonious 

 and definite conclusions. In a recent brief paper ('12 a) I have 

 reviewed the two in their relation to each other. Here I shall 

 not attempt to review the work on vegetative reproduction but 

 merely to summarize the common result of both lines of work. 



GENERAL CONCLUSION 



Comparing conjugation with the fertilization of higher animals, 

 we find the following to be the state of the case : 



In higher animals fertilization has two diverse effects, which 

 recent investigation, particularly that of Loeb and his associates, 

 has clearly disentangled. (1) On the one hand, it initiates develop- 

 ment; it prevents the egg from dying, as it would do if not ferti- 

 lized. This function of fertilization is the one that is replaced by 

 the processes which induce artificial parthenogenesis. (2) But, 

 secondly, fertilization brings about in some way inheritance from 

 two parents. When there is inheritance from but one paretit, 

 the inheritance is as it were complete; the child as a rule resembles 

 its parent in all hereditary characteristics; this is the result of 

 the so-called 'pure line' work. But when we have biparental 

 inheritance, a great number of different combinations of the 

 characteristics of the two parents are produced, so that the proc- 

 ess of fertilization is one that in this respect completely alters 

 the face of organic nature, producing infinite variety in place of 

 relative uniformity. 



These two functions of fertilization, the initiation of develop- 

 ment, on the one hand, and the production of inheritance from 

 two parents, on the other, are logically independent; they might 

 conceivably be performed at different times and by different 

 mechanisms. The fact that in many organisms the same mech- 

 anism that brings about biparental inheritance is likewise the one 

 that initiates development might from certain points of view be 



