INFUSORIA PARASITIC IN CEPHALOPODA. 187 
According to Foettinger, there exists “at times but a single 
nucleus . . . When there are several nuclear bodies these 
are merely fragments of the single nucleus. The latter, 
being capable of amceboid movements, may assume the most 
varied forms—push out extensions, become segmented, etc.” 
To this account Gonder added that the nuclear substance 
undergoes a series of vegetative changes, so far as he was 
able to follow them, like those of Opalinopsis (see infra). 
He believes, further, ‘ that those stages which we find in the 
posterior part of the cell or in the buds are the younger, 
those which take place in the anterior part of the cell the 
older.” A cycle of nuclear changes is thus to be observed in 
one and the same animal at one and the same time. At first 
there is an arrangement of the chromatin in irregular frag- 
ments of different sizes. ‘These then become converted into 
a network, which may then undergo a resolution into a 
system of strands, and finally give rise to a condition in 
which we see, once more, a number of irregular fragments. 
The net may also, it would seem, give rise to coarsely 
granular chromatin masses. Still another stage is described, 
but its relation to the others is not quite clear. It is a stage 
in which the chromatin and plastin re-arrange themselves in 
the form of a number of perfect nuclei—each with its 
membrane, network, etc. ‘lhe nuclei appear to be of very 
variable size. 
Now I am convinced that no series of vegetative changes 
in the nucleus such as Gonder describes really occurs. ‘lhe 
appearances described—and very beautifully figured by 
Gonder—have, I believe, been wrongly interpreted. 
In the living animal it is almost impossible to make out 
anything of the nuclear apparatus with certainty. It 1s, 
therefore, necessary to work chiefly on fixed and stained 
material. Unfortunately, the animals survive but a short 
time after removal from their host, no matter what pre- 
cautions one takes. It is also a necessity, therefore, to fix 
the creatures immediately after removal. Moreover, if the 
host be allowed to die the parasites very quickly begin to 
