BENNETT — ON ANTHKA CEKEUS. 211 



agree, as far as I can find, in stating that fissiparous generation oc- 

 curs either in the way described by Dalyell — by separation of a part of 

 the margin of the base — or by division from above downwards, not from 

 below upwards, as I have described." Milne-Edwards says : — " Spon- 

 taneous fissiparous generation occurs either by detachment of fragments 

 from the inferior border of the body, which, continuing to live, become 

 developed into perfect animals, or at other times division commences by 

 a narrowing or strangulation [etranglement] of the superior extremity of 

 the body, which, becoming more and more pronounced, causes a bifur- 

 cation, the branches of which complete themselves, each on its own side, 

 so as to constitute two distinct individuals. These may remain united 

 by the base, and so cause an aggregation of polypes, or may be sepa- 

 rated completely." This mode Dalyell has observed and figured in 

 Actinia. Dalyell is the only authority, as far as I know, who attri- 

 butes the separation of the fragments, in any case, to muscular action. 



How the process is effected when it occurs in the more common way 

 — from above downwards — I cannot imagine, unless it be similar to 

 ulceration in the higher animal, or else is due to muscular action. I 

 am not certain whether any definite idea of the process is expressed by 

 Milne-Edwards in the word etranglement, which I have quoted above. 

 Gosse evidently attributes it to a process of growth. He says : — " The 

 greater part of the Astrceacea increase by disc buds and spontaneous 

 subdivision, the disc of the polype gradually widening by growth, and 

 finally separating into two portions, which become independent." 

 Whatever be the means by which the separation is accomplished in the 

 greater number of cases, it was evident that, in the exceptional case I 

 have recorded, the animal absolutely tore itself into halves ; and further, 

 that the division occurred in a direction from below upwards, the re- 

 verse of that which is supposed by some to be the constant mode in the 

 class. 



I have thought the case worth recording, as affording some clue to 

 the explanation of a physiological process which is very imperfectly 

 understood, and on account of its novelty. 



Dr. Barker suggested the possibility of the animal, in the very in- 

 teresting case brought forward by Dr. Bennett, having been accidentally 

 injured at its base in its removal from its native habitat, and that such 

 injury might have been a predisposing or exciting cause of the com- 

 mencement of the process which Dr. Bennett had described, which had 

 ended in complete division of the original animal into two ; or at least 

 such an injury might, perhaps, have determined the point at which 

 self-fission originated. 



Mr. Andrews considered the process of fissiparous division of this 

 animal (common'on the rocks of the sea coast, and. very abundant in the 

 south and west) must be regarded as quite normal ; and the actual mode 

 in which the process was carried out, as described by Dr. Bennett, was 



