CIRCULATORY APPARATUS OF THE NEMERTEA, 5 
Semper (28) was the first to notice the nephridia of 
Malacobdella. 
6. ENUMERATION OF THE SPECIES INVESTIGATED AND DEscRIP- 
TION OF THE Metuop APPLIED. 
The Nemerteans are divided by Husrecut (35) into 
Palzonemertea, Schizonemertea, and Hoplonemer- 
tea. I will adhere to this division, as it seems to me to be 
more natural than that of Max Scuuttzz (11, 12), who divide 
the Nemerteans into Enopla and Anopla, the proboscis being 
armed with a central stylet or not. In regard to the fourth 
group, that of the Malacobdellide, formed by Von 
Kennex (31), I can hardly agree with the creation of this new 
subdivision, the anatomical characters of Malacobdella show- 
ing it to be a Hoplonemertean, which, probably by its para- 
sitical habit, has lost stylet and eyes, and has obtained in the 
hindmost part of its back an attaching apparatus wherewith 
to fix itself to its hosts (Mya, Pholas, &c.). The absence 
of cephalic sacs cannot be a reason for removing it from the 
Hoplonemertea, as Amphiporus hastatus, MclInt., a 
true Hoplonemertean, is also deprived of these organs. 
Of each of these three groups I have examined examples. 
All the specimens I have used are from the collection of Prof. 
Hubrecht, who with the greatest kindness not only put the 
specimens in spirit at my disposal, but allowed me to examine 
his numerous collection of microscopical slides and series of sec- 
tions. I was thus enabled to examine specimens of all the ten 
families: Cephalotricideg, Carinellide, Poliide, Valen- 
ciniide, Lineide, Langiide, Amphiporida, Tetras- 
temmidz, Nemertide, and Malacobdellide. Only of 
the genera Borlasia, Oken (emend. MclInt.) (Lineide), 
Prosorhochmus, Kef. (Tetrastemmide), and Oerstedia, 
Quatr. (Nemertide), I have not examined representatives. 
The new automatic microtome of Caldwell from Cambridge 
has very much facilitated my research. As the Nemerteans 
are animals which cannot be submitted to the usual methods of 
