58 ZOOPHYTES. 



Some of the planulac having become stationary, formed a small white 

 spot, from which a spine rose in the centre above, and radicles diffused be- 

 low, circumscribed by a perfect marginal circle. All the radicles were of 

 a dark colour. 



The progress of such nascent Sertularise is tardy. On January 5, 

 many planula?, at least 100, were in a vessel. A week afterwards, namely, 

 on the 12th, one spot, with a spine, was on the side of the vessel, and an- 

 other on the bottom about February 11. The former had generated three 

 cells, from which very minute hydrse were displayed ; and two afterwards 

 appeared, one of them from the summit, on the 16th. On both occasions 

 I was disappointed of microscopical observations, by their sudden and per- 

 manent retreat. 



On another occasion, specimens appeared prolific also in the month of 

 December. The vesicles were huddled together on the branches, 30 or 40 

 in one place. 



The stem of this zoophyte is full of a medullary substance ; and shoots 

 have arisen from sections. These shoots are always white. 



Roots have also issued, and with bifid radicles. I have been disposed 

 to conjecture the reproduction in certain cases was inverted. Thus, a 

 specimen about three inches long, having been ruptured below, was depo- 

 sited in a vessel on January 27, where it remained undisturbed in an in- 

 clined position during fifty days. A new portion, much lighter than the 

 old, had then generated from the extremity, of greater complexity than I 

 should have expected of a root. Almost the whole parts were adhering 

 to the glass, and to that part of it, which was the side of a narrow cylin- 

 drical jar. — Fig. 6. 



No hydrae ever appeared on the specimen. 



Plate XIX. Fig. 1. Sertularia thuia, prolific specimen. 



2. Twig with vesicles. 



3. Vesicle discharging its contents prematurely. 



4. Planuke from the vesicles. 



5. Nascent Sertularise from the planuke. 



6. Reproduction from the extremity of a stalk. 



Figs. 2, 3, 4, 5, are enlarged. 



