FERTILIZATION 587 



secondary nuclei, each of which appropriates some cytoplasm, forms a 

 gamete, and undergoes reduction. Active flagellated macrogametes seek 

 out and fuse with nonmotile microgametes, in contrast to the usual 

 method. The zygote retains the flagellum and reproduces its monad-like 

 self for several generations by fission. Then the offspring develop into 

 the adult vegetative Mastigella. 



Heterogamy seems to be clearly established in this amoeboid flagellate 

 by the differences in the activity of the gametocytes as well as in the dif- 

 ferences in size and motility of the gametes. Another point of interest 

 is the pedogenic reproduction of the zygote. The interpolation of this 

 asexual cycle into the life cycle bears a strong similarity to sporogony 

 in Flasnwdium and other Sporozoa. In both cases it is the asexual multi- 

 plication of the zygote before the adult stage, or trophozoite, is formed. 



A point of particular interest to cytologists and geneticists alike is 

 the origin of the gamete nuclei from chromidia. Not only here but also 

 in a number of the Sarcodina, the origin of gamete and vegetative nuclei 

 from chromidia has been reported. If the chromidial origin of nuclei 

 is a fact, what of the genetic and structural continuity of the chromo- 

 somes and of the genes.'^ Must we accept Hartmann's (1911) "poly- 

 energid" interpretations that the nucleus is really an aggregate of many 

 small nuclei, each with its sphere of influence, and that chromidia repre- 

 sent the scattered little nuclei or energids? At present we can only specu- 

 late. The problem is one of fundamental significance and is in great 

 need of further investigation. 



Chatton (1927) described a case of gametic meiosis in the flagellate 

 Faradinhim poucheti which is "exactly comparable in its progress and 

 complexity" to spermatogenesis in certain insects. Included in his out- 

 line of this process are leptotine and pachytine stages, and diakinesis 

 with tetrad rings and crosses. It is surprising that such highly developed 

 processes should be found in such a primitive flagellate, although similar 

 stages are not uncommon in ciliates and also occur in some Sporozoa 

 and Sarcodina. The wide distribution of typical meiotic phenomena indi- 

 cates that they are fundamental in nature, and it is probable that proc- 

 esses of comparable nature also occur in all forms in which fertilization 

 takes place. Meticulous examination with improved techniques will 

 throw much light on this question. 



In the Dinoflagellata a few cases of syngamy have been reported, but 



