Biparental Inheritance and Conjugation 155 



from the other member is likely to be weak and die out also. 

 This was studied with very great thoroughness, and a strong 

 tendency to likeness in this respect was found (Jennings and 

 Lashley, 1913). 



(4) A fourth respect in which the offspring of the two 

 that have mated tend to be alike is in certain structural ab- 

 normalities that often occur (Stocking, 1915). Such abnor- 

 malities are shown in Figure 44<. Frequently these abnor- 

 malities are hereditary in the family derived from one mem- 

 ber of a pair; when this is the case, the family derived from 

 the other member often shows such abnormalities also, 

 much more frequently than is the case when its mate is nor- 

 mal. 



In all respects in which the matter has been examined, 

 therefore, mating tends to make the families derived from 

 the two members of a pair more alike than they would have 

 been without it. Conjugation produces biparental inherit- 

 ance, just as fertilization does in higher organisms. 



In Chlamydomonas, Pascher 4 has recently succeeded in 

 studying the results of conjugation with respect to charac- 

 ters of a more tangible sort than those that we were forced to 

 use in Paramecium. Two species of Chlamydomonas differed 

 in form and structure in the way shown in Figure 43a, A and 

 B. In conjugation these organisms unite completely, form- 

 ing a cyst. The cyst formed by the conjugation of two in- 

 dividuals like A has no membrane and is covered with pyra- 

 midal elevations, as shown at AA, while that formed by two 

 like B is smooth and surrounded by thick membranes (BB). 

 When A conjugates with B, the resulting cyst is intermediate 

 between the two pure forms, as shown at AB ; there is a thin 

 layer of membranes, and the surface is covered with low 

 rounded elevations. 



4 Pascher, A., Ber. d. Deutsch. Bot. Oes., 1916 and 1918. 



