TRANSACTIONS OF THE SECTIONS. 601 



ovarium like the first. The number of tentacula decreases pro- 

 gressively. Another smaller species, here denominated, provi- 

 sionally, Tubnlariapolyceps, sometimes occurring in groups of 

 five hundred heads, propagates after the same manner. The 

 head is regenerated also, and under a similar deficiency. A 

 specimen had originally twenty-one tentacula, but only sixteen 

 were renovated with the second head ; and with the seventh 

 they had diminished to six. The head evidently rises as a bud 

 within the tube from below, and its origin seems dependent on 

 the subsistence of the internal tenacious matter. 



Regeneration may be eff'ected artificially, and even to re- 

 dundance, beyond the apparent provision of Nature. Thus, 

 twenty-two heads were obtained in five hundred and fifty days, 

 from three sections of a single specimen. An equal number 

 was never reproduced by any specimen preserved entire. 



3. Serttdaria, — The most luxuriant of this diversified genus 

 may be compared to leafless shrubs in miniature, composed of 

 stem, boughs, branches, and twigs, all clothed with variously 

 shaped prominent cells, the habitation of so many Hydrce or 

 Polypi, capable of protruding from them. These are generally 

 white, or of a light grey or green colour ; some more sluggish ; 

 others very vivacious, having from eight to twenty tentacula in 

 a single row, with the mouth dilating, as a cup, in the centre, 

 to absorb the prey. None exceed a line in diameter. The 

 whole product is tubular, and occupied by an internal pith or 

 animal substance, with which the polypi are connected, and on 

 the presence of which in their vicinity their survivance depends. 

 The largest hitherto obtained by the author from the Scottish 

 seas, is here denominated, provisionally, Sertularia Uber; it rises 

 nearly three feet high, by the slenderest stem, thus exceeding 

 greatly the dimensions usually ascribed to these zoophytes. 



Besides a profusion of cells, many specimens, of various 

 speciesj bear an indefinite number of vascular substances, three 

 or four times their size, or even larger, and of greatly diver- 

 sified configuration and arrangement. They are spherical, 

 ovoidal, formed as a vase or as a Florence flas|c, indented, 

 irregular, with an orifice at the summit or in the side. It does 

 not appear that all specimens of the same species bear uniformly 

 the same kind of vesicle. They abound at every season, pro- 

 bably from the nearly equable temperature of the sea, sub- 

 sisting long if undisturbed ; but their origin is never to be 

 witnessed. 



Each vesicle contains from one to thirty white, grey, reddish, 

 green, or yellow corpuscula, the number, and perhaps the 

 size, depending partly on the species of Sertularia. Howeveiv 



