196 C. CLIFFORD DOBELL. 
micronucleus in the parasites of cephalopods. Nor is a 
micronucleus described in Foettingeria. In Rhizoka- 
ryum the micronucleus is spindle shaped. Some very inte- 
resting observations have recently been made upon a form 
very closely allied to Anoplophrya by Awerinzew (1). 
He names this animal (a parasite of the marine worm, 
Ophelia limacina) Biitschliella ophelizw; and he finds 
that the micronucleus becomes visible only when the 
animal is about to divide. In Chromidina, however, 
a micronucleus is never visible at any stage during segmenta- 
tion (ef. fig. 1). 
As I have already pointed out, the chromatin particles, 
which are normally present in the cytoplasm, may in part 
represent the micronucleus. A curious formation, apparently 
from the nucleus, of similar particles occurs at a certain 
stage in Biitschliella. Another interesting feature of this 
organism is that it may undergo a simple transverse 
fission, thus combining both the method of reproduction 
seen in Chromidina and that of Opalinopsis. Biitsch- 
liella also possesses contractile vacuoles. 
Of the deeper significance of the net-like nucleus we know 
nothing. It is as yet quite impossible to say why one 
organism should possess a single compact nucleus, whilst 
others of similar size and apparently performing similar 
functions should have nuclei in the form of a net or scat- 
tered fragments. It looks at present as though it were 
immaterial how the nuclear substances are disposed in the 
cell so long as they are present. However, the matter can 
be elucidated by further research alone. 
The foregoing pages embody a small part of the results of 
the work which I did whilst occupying the British Associa- 
tion Table at Naples from March to June of the present year. 
I desire to thank the British Association Committee for their 
kindness in assigning me the Table. I wish also to tender 
