ANTHOZOA IIYDROIDA. 25 



his favourite theory ! Like the flowers of the field, the heads 

 or " Sores" of these polypidoms expand their petaloid arms, 

 which after a time fall like blighted blossoms off a tree ; 

 they do become " old in their youth, 11 and rendered hebetous 

 and unfit for duty or ornament by age or accident, the com- 

 mon trunk throws them off, and supplies its wants by ever- 

 young and vigorous growths. The phenomena are of those 

 which justly challenge admiration and excuse a sober scepti- 

 cism, so alien are they to all we are accustomed to observe in 

 more familiar organisms ; but, besides that faithful observa- 

 tion renders the facts undeniable, a reflection on the history of 

 the Hydra might almost have led us to anticipate such events 

 in the life of these zoophytes. " Verily for mine owne part, 

 the more I looke into Nature's workes, the sooner am I in- 

 duced to beleeve of her even those things that seem in- 

 credible." 



It has been observed that many of the Hydroid Zoophytes 

 emit a luminous or phosphorescent fluid ; but whether this is 

 a secretion of health and life, or the result of some partial 

 decay and decomposition, cannot be said to have been ascer- 

 tained : perhaps the facts lead us rather to favour the latter 

 supposition.""" No species has been seen luminous in its 

 natal site and when undisturbed ; but after being torn from 

 their attachments, or tossed ashore and trodden upon, or carried 

 away to the home of the experimenter and variously irritated, 

 then the tiny lamps shine forth momentarily, die away again, 

 and are not relit unless some new shock or injury is given. 

 The facts are interesting enough to be given in detail. 



* Mr. Hassall thinks it dependent on vitality, and that loss of vitality destroys 

 the phosphorescent emission (Ann. and Mag. Nat. Hist. viii. p. 343) ; but certainly his 

 observations do not prove this. [On this passage Mr. W. Thompson has favoured me 

 with the following note : " I do not think it probable that the luminosity of Zoophytes 

 is caused by ' partial decay and decomposition,' as I have, especially in the month of 

 January, 1834, and frequently since, observed many species to put forth their lights 

 vigorously a very few hours certainly within three after I had dredged them from 

 the bottom of the sea. They were not sooner looked at, as it was not dark until 

 about that time after their capture. ' Torn from their attachments ' these certainly 

 were, but they were treated tenderly, and placed in a huge vasculum or botanical 

 box, and in it conveyed to our quarters. The Zoophytes parasitic on algae, brought 

 home in the same way, made their positions known by exhibiting their tender and 

 beautiful lights."] Mr. Thompson has seen Chondrus crispus, Cystoceira ericoides, and 

 other algie, luminous in a growing state. See Ann. Nat. Hist. viii. p. 216. 



