864 4 Annelidas. 



auspices, and I am not aware that they have been recorded before in 

 detail. I give the ipsissim a verba of my journal, written while the 

 little mechanic was before my eyes. The account is an incidental 

 testimony to the adequacy for aquarian purposes of the substitute for 

 sea-water, the constituents of which I first made public in the 'Annals 

 of Natural History' for 1854. 



June 30. My large tank of artificial sea-water, marie in August last, 

 is now very rich in animal life. The stones and old shells are covered 

 with a woolly down of (probably) ectocarpus, and the whole has the 

 settled, old appearance of a natural pool bottom. Among the inhabit- 

 ants is a Sabella, which answers in all particulars to Montagu's S. 

 vesiculosa, except that it is much shorter than his specimen, being 

 about one and a half inch long, and its tube, at least the free part, 

 about two inches. The dark purple vesicles which he mentions, at 

 the tip of the gill filaments, are in mine much more conspicuous than 

 represented in his figure, that of the anterior filament on each side 

 being much larger than the rest, and forming a stout, globose and 

 nearly black ball ; the others diminish to about one-twelfth on each 

 side, where they disappear. These balls are placed on the inner or 

 upper face of the filament stem, at the point where the pectination 

 ceases, the stem itself being continued to a slender point beyond it — 

 the " short hyaline appendage " of Montagu. From their great resem- 

 blance to the tentacled eyes of the Gasteropod mollusca I have little 

 doubt that these are organs of vision ; if so the protrusion with which 

 the Sabella is furnished in this respect may account for its excessive 

 vigilance, which is so great that not only will the intervention of any 

 substance between it and the light cause it to retire,«but very often it 

 will dart back into its tube almost as soon as I enter the room, even 

 while I am ten feet distant. 



This morning T found my Sabella clean out of its tube, and lying 

 on the muddy bottom below. I was afraid he was moribund, but he 

 was actively wriggling, and his beautiful disk blossomed as widely as 

 usual, though grovelling on the sand. Some six hours elapsed, when 

 I perceived that his body was no longer naked, but enveloped in a 

 new, loosely constructed but rather tightly-fitting tube, through the 

 posterior part of which the naked tail was protruding, as yet unpro- 

 tected. It was evident the Sabella was meeting the emergency of his 

 situation by forming a new dwelling, and that he had commenced, 

 though unseen by me, by making a ring of mud cemented with a 

 gummy secretion around the neck, which ring as it increased in length 



