TUBULAEIA. 11 



an animal product as an alcyoniiim or an ascidia, whose original corpusadum, 

 planula, spinida, larva, or by whatever name may be given, which by nature 

 becomes rivetted to some solid sustaining foundation. 



The nascent tubularia thus free, and capable of selecting its position, 

 loses that faculty never to be regained and is rooted at an indefinite period 

 — sometimes in the course of one day, sometimes on the lapse of two. But 

 quiescence is essential here. Should frequent disturbance alter its place, 

 the adhesive power seems to be impaired, or the creature rendered inca- 

 pable of its exercise. The increment of those which are rooted in early age is 

 commonly much more rapid than that of others. Specimens discharged 

 from the cyst on the 1st of January, and affixing speedily, were about four 

 lines high in seven days. Those whose adhesion had not ensued were in- 

 finitely smaller. With the latter, it is not improbable that, instead of the 

 softer extremity vegetating downwards and remaining susceptible of adhe- 

 sion, it becomes invested on exposure by an intercepting epidermis. 



At the stage of early adhesion, the tentacula, which are 14 or 16 in 

 number, appear alternately set as in a higher and a lower circle ; and the 

 stem is somewhat of variable figure — both probably indicating the softness 

 of the parts or the result of it. 



All nascent Tubulariae are of the palest grey ; and for the first fort- 

 night, the length of the tentacula and general dimensions of the hydra are 

 proportionally greater than in adults. But the stem is seldom straight ; 

 sometimes also, irregularities are seen near the root, which, as already re- 

 marked, has no radicles. — Plate III. fig. 28 : The same enlarged, fig. 35. 



The head of the nascent tubularia falls after an indefinite period, just 

 as with the adult. But life is so feeble here, that the first is rarely re- 

 placed by a successor. That of a specimen bred from the ovum in April 

 1825, fell eleven days from its evolution ; but one bred in January 1841, 

 subsisted thirty-seven days, being longer than any other. 



A nascent tubularia, with a flourishing head of fourteen or fifteen ten- 

 tacula, regenerated one with only seven, which fell on the third day, and 

 was not replaced. — Plate III. fig. 39. Another, bred from an ample ova- 

 rium, was so firmly rooted in two days that its vessel might be safely 

 emptied. It had fifteen tentacula, which extended a line a week later ; 



