104 ZOOPHYTES. 



the multitude peopling a specimen, unless when projecting from the sides, 

 or perhaps when adhering to a glass vessel, which is an incident of rare 

 occurrence. 



Sometimes a profusion of oblong greenislnparticles, discharged by the 

 hydra 1 , strew the bottom of their vessel sdfir after receiving specimens. 

 Their nutritive aliment seems to be eliminated from the grosser matter 

 absorbed by them. 



The duration of the individual hydra's life, as well as the permanence 

 of the stratum, seem to be limited. Two hydras of fig. 3, survived de- 

 lineation 22 days; and one of fig. 4, survived 24 days. The physical 

 condition under which the product exists, probably prohibits the reverse. 

 In saying so, however, I wish it to be understood, as speaking of that pre- 

 cise state wherein I have beheld it. Circumstances may be so different 

 elsewhere, as to affect the duration of the specimen, though not of the 

 hydra. 



As above observed, the A ley onella is permanently affixed in firm adhe- 

 sion to the substance invested, while the Cristatella is free. In this sense, 

 therefore, it is a parasite, which cannot be the character of the other wan- 

 dering at large. The general nature and conformation of the hydra; seem 

 to correspond, but there are other prominent features in the detail of the 

 history of each, banishing all conjectures of their being kindred species. 



The hydra; have never amounted to 400 in any specimen of the Cris- 

 tatella that I have seen. Their number is indefinite both here and in the 

 Alcyonella ; but as the specimens of the latter seem constantly enlarging 

 during summer, so does this diffusion always give birth to more. Perhaps 

 when once founded, it never ceases to grow during its existence ; and some 

 specimens bear thousands. 



Perpetuation. — After vigorous advances throughout the finer part of 

 the season, the whole product manifests approaching decay towards the 

 close of autumn. Few of the hydra; are displayed in the third or fourth 

 week of October, and often in a languid state. But innumerable ova, 

 now dispersed amidst the substance of the Alcyonella, convert its natural 

 greyish aspect to a brownish shade. Though subsisting much earlier in 

 the season, it is only thus late that the ova apparently attain maturity. 



