368 GC. H. MARTIN. 
no evidence as to the period occupied by the entire process 
of conjugation, but the pair figured in Pl. VII, fig. 8, which 
were found on fixation to have reached the final stage in the 
reconstruction of the nuclei, were followed for forty-six hours, 
but it is possible that this period is largely influenced by 
external conditions, e.g. temperature. Contact is usually 
effected between two conjugants by the prolongation of the 
apical lobes, the prolongations usually shortening as conjuga- 
tion proceeds (text-fig. 6). More rarely the apical lobe of 
one conjugant may come in contact with the side of the other 
conjugant (Pl. VII, fig. 8), and a still more rare conjugation is 
purely lateral. In these latter cases the thin wall of the 
theca of one or both conjugants is dissolved away, so as to 
allow the contact between the cytoplasm of the two 
individuals. 
Stage A.—The first internal indication of conjugation is 
afforded by the macronucleus. In PI. VII, fig. 1, the macro- 
nucleus of the individual labelled A still shows the charac- 
teristic appearance of the resting nucleus with large darkly- 
staining areas, the pseudo-nucleoli. The micronucleus is 
unchanged, and closely applied to the macronucleus. The 
tentacles are partly withdrawn. 
In B the macronucleus has already taken on the coarsely 
fibrillar appearance which is absolutely characteristic of the 
stages of its degeneration during conjugation. ‘The micro- 
nucleus has left its original position near the macronucleus, 
and is preparing for the first division. 
Stage B (Pl. VII, fig. 2).—The macronuclei of both indivi- 
duals have become elongated, and the fibrillar appearance is 
more marked. ‘he dividing micronucleus in the left-hand 
individual is covered by the macronucleus. The appearance 
of the micronucleus in the right-hand form seems to present 
some analogy to the so-called “ Sichel” stage in the first 
division of the micronucleus in conjugating Paramecia 
described by Hertwig, and more recently by Hamburger. 
Stage C.—Both individuals of the conjugation shown in 
