FISSION IN NEMERTINES. 27 
in its histology, which differs from that described by Birger! 
for Carinella and its immediate allies. 
The lateral nerve-stems do not exhibit the characters 
described and figured by that author, who finds an inner and an 
outer neurilemma separated by a considerable space. In this 
lie numerous ganglion-cells, chiefly collected above and below 
the “punktsubstanz,’ which is surrounded by the inner 
neurilemma, and to which the processes of the ganglion-cells 
pass. In the present worm the ganglion-cells are very few, at 
any rate towards the middle of the worm, though they are 
more numerous anteriorly. But these cells lie not only above 
and below, but at the side of the nerve (fig. 11). Further, I 
do not find distinct inner and outer neurilemma. The nerve- 
cord is surrounded by a distinct but delicate membrane, with 
flattened nuclei (m’ m’”); this appears to correspond to Biirger’s 
outer neurilemma. The ganglion-cells are situated in a net- 
work of tissue, resembling, in general, the substance of an 
ordinary Invertebrate nerve-cord, and the meshes of this net- 
work are occupied by fine dots—the “ punktsubstanz ”’ (p.). 
Lying near the centre of the nerve-cord is a distinct tube, 
with well-marked wall, against which lie here and there nuclei 
resembling those of the ganglion-cells. This tube (ch.) usually 
appears empty, but in some sections a faint coagulum with 
very minute scarcely visible granules init. There is no net- 
work, such as occurs in a nerve-cord, and I take this tube to 
be a “ giant fibre” or “‘ neurochord,” such as Biirger finds in 
Nemertine nerve-trunks generally. 
In Carinella, according to that author, there are none, 
whereas in the Schizonemerti he finds several of them. It 
might be suggested that what I regard as the wall of a tube or 
neurochord is, in reality, Biirger’s “ inner neurilemma;” but 
the contents of this tube are certainly not like the structure 
seen in an ordinary Invertebrate nerve-cord. My sections 
were stained in picro-carmine, and others in alum carmine. 
I did not employ hematoxylin, and it is possible that a 
1¢ Unters. ub. d. Anat. u. Histol. d. Nemertinen,” ‘Zeit. fiir wiss. 
Zool.,’ 50. 
