114 



Conjugation occurs between tailed gametes (larger or smaller) and 

 non-tailed forms always somewhat and usually much, larger than the 

 tailed form (fig. 3). This has been observed many dozens of times for 

 both species. The tailed form at the time of conjugation has a single 

 nucleus. The larger, non- tailed gamete may have one large »resting« 

 nucleus, one large nucleus in process of division (fig. 4), or two nviclei, 



Fiff. 1. 



Fig. 2. 



Fis. 3. 



Fig. 1. An adult but small Opalina intestinalis with each nucleus in mitosis, eight 

 chromosomes in each end of each nucleus. From an acetic-carmine preparation in 



which the cilia were too much injured to be drawn. X 620 diameters. 



Fig. 2. A microgamete of Opalina intestinalis, from life. The clear vesicle is the 



nucleus whose chromatin structures did not show clearly enough to draw. Observe 



the spherules in the endosarc ; also the slight swelling near the end of the tail. 



X 930 diameters. 

 Fig. 3. Conjugation in Opalina intestinalis, early stage. From life. X 620 diameters. 



the posterior one often being smaller. In conjugation the fusion is usu- 

 ally complete , though in several cases I have seen gametes more than 



