DASYCHONE ARGUS. 279 
before the plume “ unfolded in nearly the natural figure *°—developed de novo on the fragment, 
the plumes on the anterior fragment being undisturbed. Having thus been successful in 
the case of a bisected specimen, he next cut a Dasychone into three fragments, anterior, middle 
and posterior, and each formed a sheath. In three weeks the middle section had generated 
a new plume about one-eighth of an inch long ; and im fifty-five days the posterior extremity, 
originally of about a dozen segments, presented eight perfect branchize and two tentacles. 
Under these circumstances Dalyell remarked that when we attempt to eradicate an organ, 
some imperceptible atom may escape destruction, and survive to enlarge in its place, but the 
same argument is inapplicable to the evolution of similar parts on another site. “ Here we 
seem to reach a postulate, demanding the indefinite—the universal diffusion of germs, ready 
for development wherever the obstacles to it cease, or of some creative power, effecting a 
secretion of such matter as may produce new organs, in form and substance.” Pangenesis 
was thus thought of before Darwin. This author likewise observed that “the tentacles 
have the power of transmitting particles up the back.” 
R. Wagener’ (1832) describes Sabella lucullana:—‘ Tubulis erinaceis, transversis, 
rugosis, inferne coalitis.’ He mentions the external processes and the pigment-spots on 
the branchial filaments. The general structure of the body is similar to that of his 
S. ventilabrum. He also alludes to Sabella nuda—a form without the processes on the filaments 
and a tube immersed in sponges and Alcyonarians, but identification is difficult. It may be 
the young of his Sabella ventilabrum. Unfortunately his figure is not diagnostic (fig. 8). His 
Sabella euplacana is a Serpulid (fig. 9) with two opercula, the ends of which have long pro- 
cesses. It may be Hydroides norvegica. He figures (fig. 10) Serpula fimbriata, Delle Chiaje— 
apparently copying Delle Chiaje’s figure. It has spinous ribs along the tube. 
Lo Bianco (1909) mentions that at Naples Dasychone lucullana, D. Ch., had a circlet of 
ova at various stages in a gelatinous matrix at the mouth of its tube—from December to 
April. This author (1893) separates D. argus (his lucullana, D. Ch.) from Dasychone 
polyzonos, Grube, the latter, however, being synonymous with Dasychone (Branchiomma) 
Dalyelli, Koll., and Dasychone argus, Sars. This confusion is avoided by the diagnosis 
adopted in this work. 
Delle Chiaje, Grube and Claparéde found that the fertilized ova are borne by the females 
like a collar in the anterior part of the tube. The development of Dasychone lucullana 
is described and figured by Claparede and Mecznikow” (1868) from the egg onward to the 
formation of the branchial filaments. In the cleavage the two larger somatoblasts pos- 
teriorly are characteristic. The larva is monotrochous, pear-shaped, with a prototroch and 
two well-marked eyes furnished with lenses. Palpocils occur on the anterior margin, and 
the alimentary region is indicated by large granular cells. 
In the next stage the body is more elongated, has three bristled segments, the eyes have 
moved inward on the dorsum so as to be nearer each other, and the rudiments of the branchial 
apparatus appear as two broad dorsal flaps. The alimentary canal shows pharynx, glandular 
intestine and rectum. Then the branchial rudiment bifurcates, afterwards becomes multifid, 
and the head-lobe is evident from the under surface. At a further stage the six or seven 
branchial filaments elongate, the body lengthens, but the eyes remain; whilst a little later, 
1 *Tsis, 1832, p. 654, taf. x, fig. 7. 
2 ¢ Zeitschr. f. wiss. Zool., Bd. xix, p. 197, taf. xvi, figs. 1—1e. 
