ANNELIDS FROM THE N.E. PACIFIC. 249 
the same. In Dendronereis, this lobation of the rami is carried 
still further (apart from the dendritic development of the 
cirtl), while in Ceratocephale and Tylorhynchus the process has 
probably not gone so far. 
Coming to the first two pairs of parapodia, we meet with a 
ditficulty, In these, in the higher forms, the notopodium, 
although without the setigerous lobe with its spine and bristles, 
is nevertheless represented by a single ligule and a dorsal cirrus. 
Well, this is a difficulty, and for the present I shall leave it 
as such. I hope to elaborate this theory further in a larger 
work. 
Text-figure 7. 
FC, 
KO PERL +PRO. 
Poly 
ae Es, 
Bre 
A. Sagittal section of anterior region of Nereis pelagica, Plymouth. 
X about 6. 
B. Micronereis variegata. Sagittal section of anterior region. 
(Diagrammatic.) XX about 50. 
PRO., prostomium; PERL, peristominm; T., IT, first and second, seti- 
gerous segments; Z., tentacle; Plp., palp; H., position of eyes; 7.C., 
position of tentacular cirri; Pp.Z., position of first parapodium. 
The severed surfaces are indicated by shading, 
And now we come to the prostomial lobe of the higher forms. 
This would seem to have been derived from the condition in 
Microneveis by the forward elongation and constricting off of the 
upper median surface of the head-region, in such a way that 
the eyes are carried forward so as to be included in the con- 
stricted-off lobe. Then on the anterior margin of this lobe 
palps and tentacles have been developed, in response to the need 
for more efficient sense-organs consequent on the enlarged ac- 
tivities and “ wider outlook on life” which the higher Nereidze 
have probably assumed, 
