452 



SIMILITUDE TO COKALS. 



Our space is so rapidly drawing to a close, that it will be hardly possible to give much 

 more than a rapid mention of the names of the next few engravings, together with a brief 

 account of one or two of the more interesting examples. 



IN the group of polyzoa given in the accom- 

 panying illustration, the reader will not fail to 

 notice the great external similarity between their 

 forms and those of the true stony corals so familiar 

 to us. It will, moreover, be found, that in many 

 details of their structure, there is a decided analogy 

 between them and the true zoophytes which will 

 be described in the latter part of the work. 



Fig. A, Plate V. represents the Crisia eburna 

 of the natural size, and just below, at fig. B, is 

 given a portion of the same species as it appears 

 when magnified. The arrangement of the cells is 

 simple and elegant, and the various branches are 

 connected with each other by means of certain 

 horny joints. The use of these joints is, in all 

 probability, to enable the polyzoary to resist the 

 action of the waves, and so to avoid the fractures 

 which would probably result if the joints were as 

 stiff and inflexible as the cells. A similar pro- 

 vision will be seen in the Gorgonia, a zoophyte 

 which will be described on a future page. 



A remarkably constructed species, the Idmonea 

 atlantica, is shown at fig. C, where it may be seen 

 looking something like a many-legged spider, with 

 its branches protruding from a rounded centre 

 which represents the body of that animal. Two 

 magnified representations of this curious species 

 are to be seen at figs. D and E, the former giving 

 the front view and the latter the lateral aspect, in 

 order to show the peculiar construction of the 

 polyzoary, and the firm manner in which the cells 

 are set upon their common basis. For the figures 

 in this and several of those of the succeeding 

 plates, I am indebted to the kindness of Mr. Busk, 

 who allowed them to be taken from his forth- 

 coming part of the "Catalogue of Marine Polyzoa." 



At fig. F is seen a small portion of a polyzoon 

 termed Pustulopora delicatula, the generic name 

 being on account of the minute dots with which 

 che surface of the cells and polyzoary is studded, 

 and the specific title in reference to the delicate 

 structure and soft brown hue with which it is 

 coloured. The same specimen is represented at 

 fig. G, much magnified, and is remarkable for the 

 profusion and great comparative length of the 

 cells. The last figure in the engraving, marked H, 

 is a stoutly-built polyzoon named Hornera, and is 

 notable for its resemblance to several corals. 



IN the species given in Plate VI. the resemblance to the corals, the madrepores, and 

 even the stony habitations of certain marine worms, is very close and striking. 



Fig A represents a polyzoon fancifully entitled Alecto, in honour of one of the Furies 

 of that name. It is seen of its natural size as it appears while spreading itself over the 



POLYZOA, V. 



A. Crisia eburna. B. Crisia ebwrua. x 



C. Idmdnea atlantica. 

 D. Idmdnea attdntica. x (Front view.) 

 E. Idmonea atlantica. x (Side view.) 



F. Pustuldpora delicatula. 



G. Pitstidopora delicatula. x H. Hornera. 



The sign X signifies that the object is magnified. 



