458 University of California Puhlications in Zoology [Vol. 20 



ward where they end posterior to the nucleus in a single basal granule. 

 Since there are ca.ses in Menoidium which present such an appearance 

 as that described by Wager, and also instances in which the flagellum 

 arises from only one blepharoplast, it seems quite possible that such 

 a double condition is produced either by the splitting of an originally 

 single structure, or else by the beginning of outgrowth of the new 

 flagellum. Also, Dobell (1908), Berliner (1909), Belaf (1916), 

 Schiissler (1917), and Rhodes and Kirby (MSS) find only one 

 blepharoplast for each flagellum. 



Paradesmose 



As the blepharoplasts become further separated in the late meta- 

 phase and early anaphase, they are seen to be connected by a parades- 

 mose (pi. 41, figs. 17-19). This structure was first described by 

 Kofoid and Swezy (1915a) in Trichomonas as a "chromatic thread 

 which lies outside of the nuclear membrane." Subsequent papers 

 (Kofoid and Christiansen, 1915^, b; Kofoid and Swezy, 19156, 1919a, 

 b, c, 1920, 1922; Swezy, 1915a, b ; Boeck, 1917; Cutler, 1919; Rhodes, 

 1919) have described such a structure in many different flagellates, 

 and it is probable that a paradesmose will prove to be a common 

 characteristic of mitosis in flagellates. It should be stated, however, 

 that in most cases the paradesmose is an exceedingly delicate structure 

 and is verj- difficult to stain and determine ; hence, many observers 

 have failed to find it. 



In Copromonas subtilis, Dobell (1908, pi. 5, figs. 44 and 45) 

 figures a fine strand connecting the two daughter 'basal granules' 

 at division; this structure resembles very closely the paradesmose 

 found in Menoidium, so that it is probably permissible to assume that 

 Copromonas also possesses a paradesmose. Dobell, however, attributes 

 no significance to this structure, merely stating that "the basal granule 

 then divides, becoming dumb-bell shaped, and finally being constricted 

 into two daughter-granules." Yet Dobell finds no rhizoplast in 

 Copromonas. It is probable, however, that a more adequate staining 

 technique would have disclosed such a structure, since Berliner (1909) 

 figures a rhizoplast in Copromonas major. 



In Euglena agilis (fig. B) I have recently found a paradesmose 

 similar to that in Menoidium; here also this structure is spun out 

 between the two blepharoplasts after their division. 



