SERTULAEIA. 167 



a short spine rising from a third. The same vessel likewise contained an 

 irregular substance, rather larger than a contracted planula, from which 

 several spines were issuing next day, and which proved to have been 

 originally some combination of the elements of young Sertularise. 



On January 13, many planulse, discharged from the vesicles of this 

 specimen, PI. XXVII., were crawling in the vessel a, above referred to 

 from which this specimen was removed next day. All the planulse were 

 converted to roots with spines on the 20th, the latter unequally advanced, 

 some being scarcely perceptible. It then appeared to me that the spine 

 was prolonged from the smaller extremity of the planula. The diffusing 

 root spreads with considerable regularity where only a single planula under- 

 goes its metamorphosis, PL XXIX. figs. 12, 13, 14, 16 ; but it is some- 

 what irregular where more than one are in approximation, as fig. 16. 



The nascent product was variously advanced on the 24th, — such as a 

 spine with a root not yet diffused, fig. 17 ; or crowned by a growing bud, 

 fig. 18 ; enlarged, fig. 19. There were also two rising from a root diffused 

 irregularly, as above, in fig. 16 ; together with a hydra, and a bud from 

 another, fig. 26 ; and one specimen with two hydrse, fig. 21. The hydrae 

 of fig. 16, had each 18 tentacula; the front of one of them enlarged, 

 fig. 1. It is unnecessary to say more of the brood in the small vessel re- 

 ceiving the specimen. — PL XXVII. originally. 



This same specimen was transferred to a larger vessel, b, on Janu- 

 ary 14, wherein many planulas appeared on the 17th, as above said. 

 Having undergone their metamorphosis, a number of nascent Sertularise 

 had two hydrae flourishing on the 31st of the month, or two and a bud : 

 and one, the farthest advanced, had three. Therefore, the specimen with 

 three, had reached this stage of maturity, from the planular state, in about 

 a fortnight.— PL XXIX. figs. 22, 23, 24. 



Certain anomalies occur among a numerous brood. The regular pro- 

 cess of propagation is the discharge of a planula from the vesicle, its con- 

 sequent activity ; the cessation of motion, diffusion of the root, and a spine 

 rising with an enlarged summit, which is next displayed as a hydra. But, 

 sometimes no sensible spine rises above the diflfusing root, thence further 

 progress is arrested ; and sometimes, though the planulse be productive, 



