I 
292 Florence Peebles. 
A. Introduction. 
In a brief preliminary note (1913), I described a small acoelous flat- 
worm found together with larger and less abundant forms, coUected in 
the early spring, from the Mergelhna, a sheltered harbor lying between 
Naples and Posihpo. Because of its dose resemblance to the species 
described by Uljanin (1869) under the name Nadina^ pulchella, I bave 
given this worm the name Äphanostoma pulchella. Among the .larger 
forms occurring in this region, two new species. ÄmpMscolops fuUgineus, 
and Monochoerus lineatus, were discovered, but the material was not 
obtained in great abundance, and for this reason it was necessary to 
abandon temporarily the determination of the systematic position of 
the second form. In August of the same year a fresh supply of Mono- 
choerus was coUected, and serial sections bave been made, in order to 
study the internai anatomy. Through the kindness of Professor Böh- 
mig of Graz, I bave had the opportunity of securing some specmiens of 
Monochoerus illardatus from Dr. Micoletzky. After comparing this 
form from the Gulf of Trieste, with the species found at Naples, I am 
convince d that the latter belongs to the newly identified genus Mono- 
choerus. In accordance with the nomenclature used by Löhner and Mi- 
coletzky (1911) I bave given the Neapohtan form the specific name 
lineatus^, to indicate the characteristic marking on the dorsal side. 
The investigation of these worms was undertaken for the purpose 
of determining, by means of various experiments, the functions of the 
sense organs, and not for histological study. As the completion of the 
experiments is postponed until a comparison of the behaviour of Euro- 
pean and American forms can be made, it seems wise at the present time 
to give a brief description of the external appearance and general struc- 
ture of these interesting species. 
Technique. 
Four different fixing fluids were employed with varying success. 
Some worms were preserved in Hermann's fluid, others in Gilson's Mer- 
curo-nitric, a third set in Zenker, and a fourth series in Corrosive-acetic. 
The latter method proved most satisfactory, although Hermann pre- 
served the musculature better than the others. Ät best these worms 
are exceedingly difficult to preserve so that the finer structures are clear. 
1 The generic name Nadina has been abandoned, as will be shown later. 
2 lineatus = striped, illardatus = flecked. 
