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EDWIN S. GOODRICH. 
It would be only necessary to carry this process a little 
further to bring about the state of things found in Dino- 
pliilus. That this interpretation is correct would seem to be 
proved by the discovery of a rudimentary separate blood- 
space in Histriobdella (Shearer [23]), and of a comparatively 
well-developed vascular system in Dinophilus by de Beauchamp 
(1). Moreover, it is quite in accord with what we know of 
the nervous system, with its distinctly segmented structure 
and metameric ganglia, and also of the development of the 
mesoblast, segmented in early stages (Schimkewitsch [20]), 
We may conclude, then, that all the Archiannelids originally 
had a normal segmented coelom. 
The Affinities of Nerilla. 
At first sight Nerilla looks like a very small Syllid. For a 
considerable time I was deceived by this resemblance, and it 
was placed among the Syllids by its early describers. If 
Nerilla were a worm of larger size its extraordinary likeness 
to a Syllid would very possibly be taken for an instance of 
mimicry, but no such significance seems attributable to the 
resemblance in this case. The deception is due not only to 
general outward shape, but also to internal structure. The 
eyes, the palps, the parapodial and pygidial cirri, and more 
especially the three prostomial tentacles, all recall the Syllid. 
Yet these cirri and tentacles differ from the corresponding 
processes in Syllids in being hollow, and the parapodial cirri 
differ also fundamentally from those of Polychaetes in being 
placed between the bundles of chaetae, and not above or 
below them. The nephridia are not unlike, and the oeso- 
phageal glands strangely simulate the paired diverticula so 
often found in the Syllidea. 
Yet there can be little doubt that the resemblance is not 
due to affinity, and that Nerilla belongs, not to the true 
Polychaeta, but to the Archianuelida. Nerilla is interesting 
because it is the most Polychaete-like of all the Archiannelids, 
and because it occupies a ceutral position among the widely 
