432 
DR. A. A. Vr. HUBRECHT. 
consists of fibrillar nerve-substance, to which a thick layer 
of nerve-cells is uninterruptedly applied. This cellular 
coating is nowhere dilated into ganglionic swellings, except 
in the brain itself. 
An important difference is presented in the situation of the 
central nervous system with respect to the muscular body- 
wall in three different groups of genera. In the more primi- 
tively organised genera of the Paljeonemertini [Carinella 
annulatay inexpectata, &c.) the whole of the nervous system 
lies directly under the epiderm outside of the muscles ; in two 
other genera of Pal;eonemertini and in all the Schizo- 
NEMERTiNi it Hes enclosed within the muscular coat of the 
body, generally between the outer longitudinal and the 
inner circular layer of the muscles, whereas in the Hoplo- 
NEMERTiNi the longitudinal marrow-trunks are situated 
inside the muscular body-wall in the body-cavity. 
Three sets of cephalic nerves originate directly from the 
brain : — a. Nerves to the tip of the snout and to the eyes (if 
present), h, A pair of nerves for the proboscis, c. A pair 
of nerves for the wall of the oesophagus and alimentary 
canal (n. vagus). ^ 
B. Peripheral Nerves, 
A rapid recapitulation of what is said about the peripheral 
nervous system ofNemertines by the three authors who have 
furnished the best original investigations on these worms — 
Quatrefages, Keferstein, and Macintosh — may precede the 
enumeration of the results arrived at by myself, and, at the 
same time, serve to explain apparent discrepancies. 
Quatrefages Annales des Sciences Naturelles,’ vi, 1846, 
p. 2T8) says, speaking of the longitudinal marrow-trunks : 
De ces troncs partent d’espace en espace des filets qui se 
portent probablement aux couches musculaires, mais que je 
n^ai jamais pu suivre assez loin pour etre certain de ce fait. 
Je n^ai distingue le long de ces troncs primitifs 
aucune trace de veritables ganglions. Seulement les filets 
qui en partent sont assez regulierement epates ^ leur base 
et quelquefois on pourrait croire qu’il y a la une sorte de ren- 
flement, mais cette particularity ne se reproduit pas d’une 
raaniere constante.” 
This is all the information he gives about the peripheral 
nervous system. I must insist upon the fact that all his 
figures (pi. 8, fig. 2; pi. 9, fig. 1) in which he represents 
the small branches springing from the longitudinal trunks 
belong to the suborder of the Hoplonemertini. In a sepa- 
rate figure of the longitudinal nerve-trunks of Carinella 
