No. 460.] STUDIES ON PLANT CELL. V. 243 



modia live. It is quite possible that the origin of sex may have 

 been involved with some of the same principles as those which 

 bring about the union of swarmers to form a plasrnodium, but 

 the added features of nuclear fusion together with the history 

 of the sexually formed cells which become in higher groups the 

 starting point of a sporophyte generation places the sexual act 

 on a very much higher level of complexity. 



There are some records of the union of several zoospores or 

 gametes to form a zygospore instead of the usual conjugation in 

 pairs. The biciliate gametes of Acetabularia (De Bary and 

 Strasburger, '77) sometimes conjugate in threes and large 

 zygotes are figured with five pairs of cilia indicating that as 

 many gametes entered into their formation. The gametes of 

 Protosiphon, described by Rostafinski and Woronin ('77) as in 

 the life cycle of Botrydium, are reported by them to unite at 

 times several together and four are so figured. Klebs ('96, p. 

 207) in his account of Protosiphon also noted the union of the 

 gametes in threes especially when in organic solutions. The 

 significance of these multiple fusions of swarm spores is not 

 clear for we know nothing of the nuclear history following the 

 union. There is in the habit, however, such a resemblance to 

 the extensive union of swarmers in the Myxomycetes as to indi- 

 cate that primarily sexuality may have been concerned chiefly 

 with cytoplasmic fusions and associated very intimately with 

 nutritive processes. I have recently observed several instances 

 of the conjugation of zoospores of Saprolegnia when the ele- 

 ments united in pairs at the ciliated ends and along the sides 

 exactly as do motile gametes, and the fused cell bore four cilia. 

 The zoospores of Saprolegnia are too far removed morphologi- 

 cally from the highly differentiated sexual organs of the group 

 to justify the explanation of such conjugation as a sexual act 

 and we must think of it as due to some peculiarities of nutritive 

 conditions. 



Another class of very interesting cell fusions, associated with 

 nutritive functions, is presented in the union of the sporophytic 

 fertile filaments (ooblastema filaments) in the cystocarp of the 

 Rhodophyceae with auxiliary cells. This phenomenon which 

 was regarded by Schmitz and his followers as sexual in charac- 



