Opalina. 285 
cysts varies from one to twelve, so probably the number of divisions 
intervening between hatching from the cyst and the formation of 
definitive gametes is not constant. We have already seen that the 
condition of the nuclei in different cysts is different, indicating that 
the time required after hatching to produce the ripe gametes may 
be different in different cases. 
As a result of the divisions following emergence from the cysts, 
two sorts of gametes are formed 1) macrogametes which do not mark- 
edly differ from the individuals of the asexual generation’) and 
2) microgametes of very minute size and peculiar form. ‘The 
macrogametes differ from the asexual forms in being smaller and in 
having relatinly longer cilia (Figs. 144, 148, Pl. XXII; 164, Pl. XXIII). 
They have one (Figs. 164—168, Pl. XXIII; 183, 185, Pl. XXIV; 210, 
Pl. XXV) or two (Figs. 170—180, Pl. XXIII) nuclei. Probably the 
typical fully mature gamete would be uninucleate, but copulation 
may occur before the final division which produces the uninucleate 
condition. The nuclear phenomena following copulation will soon 
be described. The macrogametes have large excretory organs, often 
very clearly seen in these small bodied forms (cf. Mercanr 19086). 
In the Opalinas, at all times of year, the excreta, which are for a 
time dragged behind the body, are sticky. They are no less so in 
the macrogametes (Figs. 147, 153, Pl. X XID, but this stickiness of 
their excreta is not a phenomenon comparable in any way to the 
stickiness of Paramaecium when ready for conjugation (CaLkins 1906) 
and has no relation to copulation. 
The microgametes are much smaller (Fig. 163, Pl. XXII). Their 
cilia are few in number and are long and weak. They are absent 
from the posterior end of the body, which is drawn out into a long 
aud slender tail which is bent, generally at right angles, near its base, 
at a point usually about midway in the whole length of the body. 
This bend in the tail probably aids in securing spiral movement in 
swimming. Near the tip of the tail is usually a small swelling. 
Perhaps this is always present in functional microgametes. The tail 
appears homogemous and transparent. It seems to be composed of 
ectosarc alone. It is very sticky. One imagines that the little 
swelling near the tip is a special accumulation of the sticky material, 
but the animals are so small that it is not easy to find conclusive 
evidence of this point. The stickiness of the microgametes is 
1 Qpalina has no true alternation of generations, so that this term whil 
convenient to use, is not strictly accurate. 
