ALCYONELLA. 119 



designing to carry it along with me. Such conveyance is always safely 

 and readily effected in tin cases, to be easily made in many towns, and filled 

 with water. 



In twelve days, when withdrawn from the water, the cord where en- 

 circling the bark, proved to be entirely overgrown by the Alcyonella, 

 whereby the thickness of the stratum was there augmented. The same 

 succeeded with other specimens secured in like manner. Growth had 

 been rapid, which might be probably ascribed to the profusion of mud con- 

 tinually rising from the bottom of the pond, frequently disturbed by the 

 swans, and thence affording the hydra; copious nutrition. 



This large portion of bark was finally raised, and removed on the 

 21st of September. 



Still later in autumn, myriads of ova escaped from the Alcyonella in- 

 vesting it. But after the lapse of seven months, multitudes remained im- 

 bedded in numerous channels of the bark, much resembling worm-holes, 

 such as we see in wood. Here they were arranged in straight or slightly 

 curving lines, in a single row, composed of an indefinite number. 



Though apparently oval, from the nature of their position, the ova 

 were circular, of lenticular form, the middle yellow, environed by a brown 

 circumferential ring. When removed, a number of depressions in the 

 bark, whereby the ova lay rather below the surface, indicated the excava- 

 tion of the places they had occupied by some peculiar corrosion, if not the 

 previous work of insects, figs. 13, 14 ; ova in situ, fig. 15, enlarged. 



Some of the young brood were hatched from such ova on May 9. 

 1838. They became very numerous in June, and perhaps more were 

 hatched in July, if not in the earlier part of August. Thus they had re- 

 quired a long time to attain maturity, fig. 16. 



The hydra of the young brood being pure white, their interspersion 

 with the ova yet entire amidst the dark coloured bark, offered a singular 

 contrast. Those examined in August had about 32 tentacula, whereon, 

 but only in a certain position, a double row of cilia could be discerned, 

 whose action by the one striking upwards, and on crossing the summit strik- 

 ing downwards, corresponded with those of the hydra? belonging to the 

 Alcyonella stagnorum, fig. 17. 



