458 Mrs. Thynne and Mr. Gosse on the Increase of Madrepores, 



tacles, though very abundant in number, are shorter and more 

 slender than those of the adults. 



47. When the adult Madrepores become old or unhealthy, 

 the tentacles diminish in number ; those nearest the mouth dis- 

 appear first. I have had some with only one circle on the outer 

 edge. They do not live long in this state ; perhaps one reason 

 may be that they have fewer means of procuring food. 



48. I was formerly rather surprised at the very different sizes 

 of the adult Madrepores. I have some with the polypidom not 

 more than a quarter of an inch in diameter, and I used to con- 

 sider whether they could be juveniles ; but sometimes the height 

 of the stem [column] seemed to preclude such an inference, and yet 

 in all save size they appeared alike. Now I fancy I understand it. 

 They probably divide as long as possible ; and occasionally, from 

 roughness of the rock, some very small portions are left, with 

 perhaps not six of the old tentacula (I had one with only three 

 of the old tentacula, and yet it became perfect) ; then, when by 

 the law of their nature they are compelled to fix their habitation 

 for life, such little creatures can only form or require propor- 

 tionate polypidoms, though they are quite as old, and of the 

 same species, as those of larger size. 



Annotations on the above. By P. H. Gosse. 



In the foregoing observations, Mrs. Thynne has assumed that 

 the two animals whose growth and repeated subdivision she has 

 so graphically sketched were Madrepores of the species so com- 

 mon on the Devonshire coast, and known to naturalists as Cya- 

 thina (or Caryophyllia) Smithii, On reference to § 7, we find 

 that she did not actually witness the origination of these two 

 specimens, but found them, in a very infantile state, on a piece 

 of rock which had been introduced into her aquarium sub- 

 sequently to the original Torquay Caryophyllia, The growth 

 of Madrepores through a period exceeding two years, and the 

 attainment by them of dimensions far exceeding those of any 

 specimen of undoubted Caryophyllia on record, without the least 

 apparent tendency to form a corallum, were facts so new and 

 strange — to me at least — that I could not help scrutinizing with 

 some scepticism the evidence of the assumed identity of species. 



Moreover, I had by me some coloured drawings which I had 

 carefully taken from the specimen of Corynactis heterocera which 

 Mr. Thompson had described in the ' Annals of Nat. Hist.' for 

 April 1855, and was forcibly struck with the resemblance borne 

 by Mrs. Thynne's figures to that soft-bodied Caryophylliacean, in 

 size, form, colour, and general appearance and arrangement of 



