46 The Ohio Naturalist. [Vol. X, No. 3, 



In almost every cell in which there are several of these 

 amoebulae they may be seen to become associated in pairs, 

 (Fig. 4), coming into closer and closer contact until the plasma 

 membrane between them breaks down and the cytoplasm 

 of the two fuses (Figs. 5, 6). All stages in this conjugation 

 except the disappearance of the plasma membrane are verv 

 easy to observe, many dozen of them being found in mv 

 slides. The nuclei, however, do not fuse though they may in 

 the early stages lie close together. Immediately after conjuga- 

 tion which seems to take place soon after the amoebulae have 

 entered their host, growth begins and seems to proceed rather 

 rapidly judging from the fact that conjugating forms are much 

 more abundant than such stages as are shown in Figs. S and 9, which 

 immediately follow. Without any further change in structure 

 the zygote continues to grow until it has completed its active life 

 when it encysts and becomes a binucleate resting spore. 



Though there are frequently two or even more than two 

 zygotes in a single cell all of the amoebulae do not succeed in 

 conjugating. Such as fail become large coenocytes which ulti- 

 mately segment into zoosporangia. The very early stages in the 

 division of the nuclei of these zoosporangia are so minute and 

 difficult to follow that one can hardlv be certain of the correctness 

 of his conclusions. But apparently the nucleus fragments by 

 constriction into about four daughter nuclei while the parasite is 

 yet very small (Fig. 13, a). These do not further subdivide until 

 a considerable enlargement both in nuclei and cytoplasm of the 

 parasite has taken place. (Fig. 13, b). Such quadrinucleate 

 parasites arc fairly abundant and from this stage on the course 

 of development is easy to follow. The parasite increases from 

 10—15//, usually to about 7()/{ and the nuclei multiplv until thev 

 become oceedingly numerous and very minute (Figs. 14-17). 

 No spindles were observed at any time in this process of multi- 

 plication, while some clear cases of amitosis were seen (Fig. 14). 

 The nuclei are so minute however, that it cannot be stated pos- 

 itively that amitosis is the sole method of nuclear division. At 

 the end of this vegetative period the C3'st segments into a zoo- 

 sporangium (Fig. 18), with an immense number of spores so 

 minute ("2.5//) that their finer structure cannot be made out. 



In the intermediate stages of the active cycle both of the 

 resting spores and the zoosporangia there is a strong tendency for 

 the vacuoles of the cytoplasm to coalesce to form one large cen- 

 tral vacuole (Figs. 14-17), traversed only by very fine strands of 

 cytoplasm. This central vacuole may appear very early (Fig. 14) 

 or it may not appear at all (Figs. 9-13). During these stages also 

 refringement deeply staining granules frequently appear on the 

 strands of cytoplasm (Figs. 11, 16). These resemble closely the 



