GONOMENY— UNION OF GAMETE8 



83 



anotlier, and unite first by their anterior ends near the flagellar origin 

 (Figs. 42 and 48). During this process the flageUates are actively motile. 

 Their nuclei approach one another and come into contact, and the nuclear 

 membrane disappears at the line of contact till a common membrane is 

 formed. In the case of Cercomonas longicauda, Woodcock (1916) observed 

 union to take place first near the posterior end (Fig. 41). 



Union of gametes within the gametocysts of gregarines takes place 

 in a similar manner. As already explained, sometimes the gametes are 



Fig. 48. — Syngamy of Copromonas suhUlis ( x ea. 



1. Individual flagellate as seen in living condition. 



3. Nuclei dividing to form tirst reduction body. 



4. Nuclei dividing t(i fmin sccdud ivdurtion body. 



5. Union of nuclei and formation nfcNst 



2.000). (After Dobell, 1908.) 

 2. Early stage in union of gametes. 



6. Fully formed zygote in cyst. 



alike, and are merely spherical bodies which, coming into contact with 

 one another, gradually fuse, while their nuclei unite. In other cases the 

 gametes produced by one gregarine are elongate and provided with 

 flagella, as in StylorhijncJms, while those produced by the other are spherical 

 bodies (Fig. 482). Union takes place by one of the elongate flagellated 

 gametes attaching itself to one of the spherical forms by its pointed 

 anterior extremity, after which fusion takes place, while the flagellum 

 disappears. Amongst the coccidia the minute flagellated microgamete 

 swims activelv and comes in contact with one of the larger immobile 



