No.416.] PROTOZOA OF ESPECIAL INTEREST. 647 
(the last two parasites on Hydra fusca), Vorticella, Zoótham- 
nium, Epistylis. Finally, the Suctoria are represented by the 
two genera Spharophrya and Podophrya. 
Turning now to the less frequently observed forms, there is, 
in some cases, apart from the fact that they may be found at 
Van Cortlandt, little to be said in addition to the existing well- 
known descriptions. A few remarks as to their mode of life 
and relationships, however, may not be out of place. 
Nuclearia delicatula Cienk. 
This form, which was first described by Cienkowsky, has 
occupied rather a varied position in classification. Placed by 
some writers with the Heliozoa, by others with the Rhizopoda, 
it belongs to those forms which, in any artificial classification, 
must be considered as individuals rather than in groups. The 
peculiarity of Nuclearia lies in the fact that its pseudopodia, 
while long and needle-like, and in this respect similar to those 
of the Heliozoa and the Radiolaria, are at the same time very 
changeable, like those of the Rhizopoda. When the needle- 
form pseudopodia are drawn in, the organism moves along like 
an Amoeba and changes its place much more rapidly than the 
Majority of the Heliozoa. When not moving, the animal 
thrusts out its fine ray-like pseudopodia to a distance equal to 
one and a half times its body diameter. The animal is rest- 
less, however, and retains this condition only a short time, 
moving off soon with an elongate form and by means of its 
ameeboid processes. Unlike the fine ray-like pseudopodia of 
the common Heliozoa, the appendages of this form have no 
axial filaments to give them rigidity, and they frequently branch 
and sub-branch, while the animal is moving (Fig. 1, B). In 
this condition it surrounds and ingests food particles of various 
kinds, especially plant cells, euglenoids, etc. I had a very 
good culture of Nuclearia last year, and had studied the little 
Organism rather carefully for several days, devoting many 
hours to their mode of life, etc., but I had not seen one divide. 
One day I had a very fine specimen under an immersion lens, 
when a colleague, who was born under a lucky star, came in. 
€ had not watched the specimen five minutes before he 
