SEX IN PROIOZOA 137 



Order Cryptovjonadina 



No instances of sexual reproduction in this group have been 

 found. 



Order Fby tovioiiadiim 



This group inckides the chlaniydonionads and volvocids that are 

 discussed by Dr. Le^in in this volume. They will not be considered 

 here except to state that sexual reproduction is extensively represented 

 in the group. 



Order Engleiioidma 



Perhaps the most frequently referred to account of syngamy in 

 the euglenoids is that of Dobell (1908) for the colorless Copromonas 

 subtilis (Fig. B, 1 to 8.) Cytoplasmic fusion of ordinary individuals 

 is followed by two meiotic nuclear divisions after each of which one 

 daughter nucleus degenerates. The haploid pronuclei fuse to form a 

 diploid nucleus. The zygotes usually encyst but may not before 

 resuming normal vegetative activity. This life cycle was confirmed 

 by Berliner (1909) for C. viajor and by Woodcock (1916) for C. 

 niviinant'nnu, and I have seen such cell fusions in my own cultures in 

 which C. subtilis had developed. However, the absence of any chro- 

 mosome determinations or other mitotic details leaves the accounts 

 incomplete and therefore unsatisfactory. 



Haase (1910) described syngamy between amoeboid gametes of 

 reduced size in Euglena sangiiiiiea, but the descriptions are not con- 

 vincing, and later students of this species including Alainx (1928) 

 and Giinther (1928) could not confirm the findings of Haase and 

 discounted her interpretations. Biecheler (1937) in France reported 

 fusion of vegetative cells of an undetermined species of Engleiia. 



Krichenbauer (1937) found individuals of Phacjis pynnn with 

 two nuclei of different size, the smaller one being more heavily stained 

 (Fig. B, 9, 10). He also found stages indicating nuclear fusion (11, 

 12). In a cell stained with Feulgen, a large nucleus seemed to show 

 diakinesis (13). Tw^o nuclear divisions (14, 15) were followed by 

 division of the cell into four daughters. Krichenbauer saw four-part 

 divisions many times among living specimens of Fhacus caudata. He 



