THE NEMATOCYSTS OF TURBELLARIA. 273 
As regards the function of the proboscis in these forms 
there seem to be two divergent views: (1) Hallez regards 
the proboscis mainly as an organ of prehension for seizing 
the animal’s prey, and in his account of Gyrator notops 
the following passage occurs: “Si l’on place sur le porte- 
objet d’un microscope quelques Gyrator, avec des Cyclops, 
on ne tarde pas a voir, a la premiére rencontre, le Gyrator 
devaginer sa trompe et fixer lentement sur sa victime 
Yepithelium adhésif de son organe de préhension.” Hallez 
describes rhabdite-like structures in the proboscis, to which 
he is inclined to attribute an adhesive function. (2) This 
view is strenuously denied by von Graff in his monograph. 
He asserts that the proboscis functions only as a tactile organ. 
If we regard the proboscis as a purely tactile organ it is very 
hard to explain its enormous muscular development in such 
forms as Polycystis goettii, negelii, Gyrator, ete. 
The base of the proboscis consists of an enormous mass of 
muscle to which are attached long powerful retractor muscles. 
I have myself seen both Polycystis goettii and Poly- 
cystis negelii capture Copepods with their proboscis. 
In one case in which a Polycystis negelii had captured 
a large Copepod in this manner, it bent round and started 
swallowing the posterior thoracic feet, which seemed para- 
lysed, although the violent movements of the gut and the 
anterior appendages showed that the animal was still alive. 
ALLOIOC@LA. 
Allostoma monotrochum.—As far as I know only 
three specimens of this form have been found by von Graff, 
in 1879, in Trieste. He describes it as possessing oval 
bodies in the skin from 0:003—0:004 mm. long, with the 
appearance of a coiled spiral thread which, however, he never 
saw ejected. 
