Observations on British Zoophytes. 441 



scribed the occurrence of certain vesicles on the branches of 

 the Coryne exima, which, although possessing a strong re- 

 semblance to the reproductive sacs of the zoophyte, and 

 formed of all the proper tissues of the coenosarc and its 

 coverings, were distinguished from those organs by each 

 enclosing a single living Pycnogon, which, in the smaller 

 vesicles, was embryonic, while in the larger it presented an 

 advanced stage of development. A similar observation was 

 made by Mr G. Hodge (Ann. and Mag, N. Hist., ser. 3, vol. 

 ix.), who considered that the sacs were modified or stunted 

 branches of the Coryne, the development of which had been 

 arrested by the presence of the enclosed Pycnogon. On read- 

 ing the papers of these gentlemen, I remembered that I had, 

 some time before, been much puzzled by the discovery of 

 armless Pycnogons resembling Mr Hodge's figure (pi. iv. 

 fig. 10, op. cit.) in several altered polyps of a specimen of 

 Hydractinia. In this case two or three were found in each 

 polyp, which had assumed the form of a dilated and trans- 

 parent sac crowned by its usual tentacles. The polyps ap- 

 peared to be bloated and overgrown under the use of their 

 Pycnogon diet. Mr Hodge's paper at once set me on the 

 look-out for another specimen of Hydractinia tenanted by 

 Pycnogons, and this I at last obtained by the kindness of my 

 friend, Dr Wilson, Demonstrator of Anatomy at the Univer- 

 sity of Edinburgh. In this, one of the polyps contained 

 three larvae of a pale yellow colour, which appeared, as far 

 as could be seen without injuring the polyp, to be destitute 

 of legs. When first observed, the polyp was furnished with 

 its proper complement of tentacles ; but as the development 

 of the Pycnogons proceeded, the tentacles were absorbed, and 

 the polyp became a long sac pointed at its upper extremity, 

 and fitting closely on its contents, which appeared to be em- 

 bedded in the longitudinal folds of the highly-developed 

 endoderm. Mr Hodge supposes that the larva?, at a very 

 early stage, are swallowed by ordinary alimentary polyps 

 of the Coryne, and carried through the tubes of the coeno- 

 sarc, until they arrive at a part which is about to become a 

 polyp, which thereupon has its destination altered. And 

 I think there can be little doubt that his surmise is correct, 



