156 Zoological Society. 



First, as to size. The dimensions given in my previous com- 

 munication were those of the largest polypes that I had seen alive, 

 which were described as being from 2 to 3\ lines in height by 

 about 1^ in breadth ; such also is the size of many that I have 

 seen since ; but among them have been several examples in which 

 these measurements have been nearly doubled, and with the increase 

 of size a power of varying the shape of the body has been exhibited, 

 almost equalling that of Corynactis, so well known for the remark- 

 able changes of form that it undergoes. This mutability of shape is 

 dependent in a great measure on the degree of density of the external 

 coating of sand, which does not increase in proportion to the growth 

 of the animal ; so that while the half-grown polype is closely im- 

 prisoned in its hard covering, older and larger individuals are less 

 thickly clothed ; and when in a state of expansion, the grains of 

 sand are sufficiently separated to allow the integument to be seen 

 between them, and thus to permit that mobility of body which is so 

 characteristic of the Zoanthidce. The rigid form in the first spe- 

 cimens that I examined, was one of the difficulties that I met with 

 in identifying them with Mr. Couch's description of the species. 



There are some other points of disagreement which I have little 

 hesitation in saying are due to a misconception on the part of Mr. 

 Couch when preparing the original description. I refer especially 

 to the statement that " the surface of the body is minutely glan- 

 dular," and that " radiating from the mouth are numerous rows of 

 whitish glandular-looking bodies, which are the tentacula in a con- 

 tracted state ; " in both these cases it is evident that the character 

 of the sandy covering has been misunderstood. Secondly, as to the 

 growth of the basal membrane. I have previously referred to it 

 under the linear and expanded forms, which I then ventured to think 

 were only modifications in the development of one species : the re- 

 cently captured specimens throw some further light on the subject. 

 Among various groups on one large shell, I have found lines of po- 

 lypes sometimes sending out lateral shoots from the basal membrane, 

 and these again dividing ; others expanding, so as to include two or 

 three polypes in parallel series, and in one instance a single specimen 

 was observed with the basal expansion extending equally on every 

 side : again, the membrane leading from a group spreads at times 

 over the surface of the shell in an irregular manner for a consider- 

 able distance, without any bud arising from it ; so that no special 

 form of growth can be considered as characteristic of the connecting 

 membrane in this species. The rate of development in the members 

 of a group is also of the same uncertain character — a large polype 

 being occasionally followed by a very small one, and that succeeded 

 by two or three of intermediate but varying size ; in fact, except in 

 certain characters, the development of this Zoanthus is subject to 

 great irregularity ; and the cases above mentioned appear to me to 

 confirm the opinion that I have before expressed of the specific iden- 

 tity of the linear form of growth with that which has been found 

 in the Northern seas, overspreading the entire surface of small uni- 

 valves. 



