ANTHOZOA HYDROIDA. 17 



by Van Beneden free or motive buds, because, although pro- 

 duced in ovisacs, they are but a prolongation or extension of 

 the common pulp of the parent polype. They are produced 

 by all the Tubularinaj from the little coloured bulbs or grape- 

 like clusters which, at fit seasons, pullulate from the bases of 

 the tentacula ; and they are also produced by the Campanu- 

 lariadse in their ovarian vesicles. It has not been ascertained 

 that any other zoophyte produces them. 



The changes which these motive buds suffer in their deve- 

 lopment are amongst the most remarkable of the secrets of the 

 deep waters that naturalists have unveiled. Sir John Graham 

 Dalyell was the first to lift the curtain ; and although I am 

 not in a position that enables me to chronicle the observations 

 of others on this point, yet it may safely be said that for the 

 full knowledge of the secret we are indebted to Professor Van 

 Beneden of Louvain. In detailing some experiments on 

 Tubularia indivisa. Sir J. G. Dalyell tells us, that, so soon 

 as the bud has fallen from its crested head, slight pro- 

 minences, enlarged at the tips, pullulate from the under 

 surface, and the " nascent animal," elevating itself on these 

 rudiments of the tentacula, as on so many feet, enjoys the 

 faculty of locomotion. " Apparently selecting a site, it re- 

 verses itself to the natural position with the tentacula upwards, 

 and is then rooted permanently by a prominence, which is the 

 incipient stalk, originating from the under part of the head. 

 Gradual elongation of the stalk afterwards continues to raise 

 the head, and the formation of the zoophyte is perfected.''"'''^ 

 Again, in his account of Laomedea dichotoma. Sir John in- 

 forms us that it rarely produces vesicles. When present, they 

 contain from twenty to thirty greyish corpuscula with a dark 

 central nucleus. " At first, all are immature and quiescent, 

 but motion at length commences : the corpuscula become more 

 distinct ; several slender arms protrude from the orifice of the 

 vesicle, which are seen in vehement action, and, after many 

 struggles, an animated being escapes. But this has no rela- 

 tion either to the planula of the Sertularise, or the corpuscu- 

 lum of the Flustra, Alcyonium, or Actinia. It might be 

 rather associated with the Medusarise. Before ascertaining 



* Edin. New Phil. Journ. xvii. p. 412. 



