No. 416.] PROTOZOA OF ESPECIAL INTEREST. 6 
57 
perhaps to the side, perhaps on top ; wherever the prey may 
be drawn, however, it is gradually worked downwards by the 
tentacles to the underside toward the mouth, and then with a 
single swallow it is transferred to the waiting endoplasm in 
which it is digested. So insatiable is the appetite of this form 
that, after adding water containing Halteria in abundance, I 
have seen it swallow in the manner described above no less 
than ten individuals within half an hour, after which its endo- 
plasm appeared filled with foreign bodies, as Von Erlanger 
described in the form he observed. 
This then is the function of the tentacle, a food-catching 
organ or set of organs ; the trichocyst which Von Erlanger 
described, or its analogue (I was unable to make it out as 
described by Erlanger), brings down the prey, and the tentacle, 
by shortening, fetches it to the mouth. The tentacle itself is 
inserted in the Halteria, for it can be seen with the greatest 
distinctness when the victim becomes quiet, and I believe that 
the dart at the end as described is not discharged into the 
prey but is driven into the soft body of the victim as a minute 
spear, with shaft attached. 
When fully fed or when warmed by artificial means the 
animal detaches itself and draws in its tentacles. It then 
swims mouth first in a rambling sort of way, turning the while 
on its longer axis (Fig. 3). ! 
Apart from the general biological interest which such an 
organism has, there is a considerable interest from a theoret- 
ical point of view. Maupas maintained in 1881 that the Ciliata 
have been derived from the Rhizopoda through the Suctoria, 
and that the tentacles are to be compared with pseudopodia, 
While the forms with both cilia and tentacles were considered 
intermediate. So important was the group of tentacle-bearing 
forms considered that Mereschowsky formed a special group — 
the Suctociliata — for their reception. Neither Maupas, Entz, 
nor Mereschowsky could regard the tentacles in these forms as 
food-taking organs similar to those of the Suctoria, and could 
assign them no function other than that of assisting inthe capture 
of aliments. As well known, the tentacles in the Suctoria are 
for the most part hollow, and the food is taken in some manner 
