Alcyonella. 
Z. ASCIDIOIDA. 
315 
The Alcyonella, if I have correctly sorted the synonymes, was disco- 
vered by Trembley in the spring of 1741. It seems necessary to give a 
copy of his figures here, (wood-cut, No. 48,) since on them is founded 
the second variation of the species, and they exhibit it in a guise very 
different from that represented in our Plate xliv. His history of the 
animal is marked with much of that excellence which distinguishes 
the inquiries of this naturalist. He correctly describes the connec- 
tion and relationship between the polype and the common mass ; the 
arrangement of the tentacula, and the structure of the alimentary 
canal, although he failed to detect the anus. He overlooked the 
cilia of the tentacula from employing magnifiers of too low a power, 
and attributed the whirlpools created in the water by their play to 
the motion of the tentacula themselves, which he says were also used 
separately to force the animalcular prey into the mouth. He knew 
that the polypes were not contractile, and believed their retraction 
within the tubes was dependant on the play of a muscular thread 
which descended from the body in the common mass. The gemmi- 
parous mode of increase in the polypidom is also detailed with some 
minuteness, but he had not seen the ova, at least in a state of ma- 
turity.* 
Immediately after Trembley’s discovery, Reaumur and Bernard de 
Jussieu found this animal in the neighbourhood of Paris, and detect- 
ed its ova, from which they saw the young issue. Reaumur’s ac- 
count of the growth of the compound animal appears to me to cor- 
roborate the opinion of the sameness of the Plumatella and Alcyonella. 
He says that while the polypes a panache are still very young, they 
increase in the same manner that the locomotive polypes do, with 
one difference only which it is essential to note, since it explains 
clearly the formation of those polypidoms that resemble plants. The 
tube of a newly evolved polype continues as it were permanently 
grafted upon the tube of that which has given birth to it : from the 
polype tube he has seen germinate by little and little another which 
contained a nascent polype ; he has seen this tube elongate itself, and 
the polype tenant at length show itself outwards to follow out the 
destined tenor of its life. Scarcely had a few days passed until this 
again gave birth to a young one whose tube was in connection with 
* It is even doubtful whether the bodies he took for immature ova were 
really so. “ J’ai vu dans plusieurs des Polypes a panache, sur lesquels j’ai fait 
mes observations, de petit corps spheriques de differentes grandeurs, blancs et 
transparens. J’ai seulement soup^onne que ces petits corps etoient des oeufs, 
mais je n'ai pas eu occasion d’examiner si ce soup9on etoit fonde, ou non.” p. 
219 , 
