NEMERTINES OF PLYMOUTH SOUND. 3 
size, one on each ventral brain lobe just posterior to the ventral 
commissure. In the centre of each capsule was a single refringent 
otolith ; no cilia could be detected. Like the two previous writers, 
with whose accounts I was not at that time acquainted, I failed to 
identify the bearers of these interesting structures. They were 
unfortunately lost before I had completed my examination of them. 
The following points, however, were made out :—Length from 1 to 2 
em. ‘T'wo of the specimens were pure white, the third was pinkish 
posteriorly ; brain conspicuously red ; head rounded, with oval trans- 
parency in dorso-median line; generative organs ripe. Proboscis 
long, reaching to end of body, with anterior terminal pore, with 
median stylet and two accessory capsules, one contaiming several 
reserve stylets, the other only two ; mouth in front of ganglia ; eye- 
less. It seems to me very probable that Burger, du Plessis, and 
myself have found the same species, since not only are the otocysts 
precisely the same in structure, but the accounts of the worms them- 
selves, though meagre, are in agreement, and all of them are found 
living under the same conditions. Du Plessis attempts to correlate 
the presence of otocysts with the absence of eyes, but the latter 
condition is not infrequent among Nemertines, while the rarity of 
those with otocysts is sufficiently evinced by the general scepticism 
with which their existence has been regarded. Joubin, inhis Poliopsis, 
describes structures which he at first took for otocysts, but afterwards 
found to be the blind ends of the ciliated canals of the side organs. 
The otocysts above mentioned cannot, however, be thus explained away. 
The classification of the Nemertines has until lately been very 
defective. In 1890 Biirger, in his admirable paper on the anatomy 
and zoology of the Nemertea (5), very ably criticised Hubrecht’s 
system, which he showed to be untenable, and proposed temporarily 
to return to that of Schultze. In the following year (6) he brought 
out a new scheme dealing with the primary subdivisions only. In 
his system these are four in number, and are based upon the 
situation of the nerve-stems. Last March (7) this system was further 
developed and carried into detail as regards three of the subdivisions. 
One of them, however, that corresponding to the Hnopla of Schultze, 
was left for a future paper, which as far as I am aware has not yet 
appeared. 
As this classification will be the one here adopted, it may be well 
to state at once its leading characters. According to Biirger’s 
scheme the whole group consists of the four following orders : 
I. PROTONEMERTINT (Carinella, Carinina, and Hubrechtia).— 
Lateral nerves outside the circular muscular layer, situated either in 
the epidermis or beneath the basement membrane. 
